OPINION OF THE COURT
GIBBONS, Circuit Judge:The plaintiffs, inmates of Philadelphia’s Holmesburg Prison, appeal from a judgment dismissing their amended class action complaint, which seeks injunctive relief against that institution as well as money damages for the conditions of confinement in same. The plaintiffs originally filed a pro se complaint which was later amended after the appointment of counsel. The trial court dismissed at the pleading stage because of the possibility of relief under the terms of a judgment rendered in a case pending in the Court of Common Pleas of Philadelphia County. We reverse.
I.
Proceedings in the Trial Court
In February of 1971 five inmates of the Philadelphia Prison System brought on behalf of themselves and others a class action in the Court of Common Pleas seeking equitable relief on federal constitutional grounds. That court found the Philadelphia Prison System to be operating in violation of the eighth amendment prohibition against cruel and unusual punishment. In August of 1973 the Commonwealth Court affirmed that holding but modified the Common Pleas Court order insofar as the earlier order required the appointment of a master to prepare a report and recommendation for the framing of a final decree. Hendrick v. Jackson, 10 Pa.Commw. 392, 309 A.2d 187 (1973). The Supreme Court of Pennsylvania, in July of 1974, reinstated the provision in the decree providing for the appointment of a master. Jackson v. Hendrick, 457 Pa. 405, 321 A.2d 603 (1974). In March of 1976 the Common Pleas Court issued its first remedial order, which, inter alia, established a maximum inmate capacity for the Philadelphia prisons. That limit on inmate capacity, as well as other contested features of the remedial order, was affirmed per curiam by the Commonwealth Court in October of 1977. Hen-drick v. Jackson, No. 1385 C.D.1976 (Pa. Commw. Oct. 17, 1977). The Common Pleas Court retained jurisdiction over the action. Between February 4, 1977 and June 29, 1983 the parties agreed upon a series of consent decrees dealing with various methods for alleviating the overcrowded conditions of the Philadelphia prisons. The Common Pleas class action did not seek damages, and the remedial decrees made no provision for individual relief for any inmate. The defendants in that action are officials of Philadelphia, not of the Commonwealth. On at least one occasion those Philadelphia defendants were held in contempt, and fined, for failure to comply with various aspects of the consent decree.
In April of 1982 the plaintiffs in the instant case, none of whom were incarcerated before April 1980, filed a pro se complaint in federal district court seeking damages and injunctive relief for themselves *341and for a class consisting of all persons who have been inmates of Holmesburg since that date, and on behalf of future Holmesburg inmates. The amended complaint alleges that since April 30, 1982 members of the class have been deprived of rights guaranteed to them by the eighth and fourteenth amendments, in violation of 42 U.S.C. § 1983 (1982). The amended complaint acknowledges the provisions of the several litigated and consent decrees which have been entered by the Common Pleas Court, but alleges that those decrees have never been obeyed. Plaintiffs allege, for example, that the Common Pleas decree fixes the maximum capacity of Holmes-burg at approximately 700 inmates, but that the current population exceeds 1300. Plaintiffs allege that, as a result of such overcrowding, they have been subjected to and injured by a long list of hazards and deprivations, and have been subject to physical and psychological injury from violent attacks, sexual assault, and threats of physical violence by other inmates. They allege further that each of the defendants, with full knowledge of the existence of unconstitutional conditions of confinement at Holmesburg, has acted or failed to act in such a way so as to exacerbate the overcrowding and resulting conditions at that institution. The defendants include the Philadelphia officials directly responsible for Holmesburg’s operation, as well as two state officials, Jay C. Waldman, General Counsel for the Commonwealth and Ronald J. Marks, Commissioner of the Pennsylvania Bureau of Corrections. The Commonwealth defendants are alleged to be responsible for establishing standards for county jails and prisons, and to have made decisions respecting classification of prisoners which resulted in the overcrowding at Holmesburg.
The Philadelphia and the Commonwealth defendants moved to dismiss under Fed.R. Civ.P. 12(b)(6).1 The trial court granted these motions. The court ruled that as against the Philadelphia defendants both the claims for injunctive relief and for money damages were barred by res judicata, having been merged in and therefore barred by the decrees of the Court of Common Pleas. As to the Commonwealth defendants, who were not parties to the Common Pleas action, the court ruled that all claims against them were barred both by the eleventh amendment and by qualified official immunity. Alternatively, the court ruled that because of the pendency of the state court action it should abstain from adjudicating any aspect of the case and, accordingly, dismissed it entirely.
II.
Res Judicata
As we noted above, the Common Pleas Court action did not litigate any claims for money damages. Nor did it litigate events occurring after April 30, 1982. Thus the Philadelphia defendants do not urge that the plaintiffs are collaterally estopped either factually or legally — barred by issue *342preclusion — because of any determination made by the Court of Common Pleas. See Restatement (Second) of Judgments § 27 (1982). Indeed, quite the opposite is the case. The present plaintiffs, who were not inmates of Holmesburg at the time of the 1972 litigation, will contend, if the case goes to trial, that the Philadelphia defendants are collaterally estopped from attempting to defend the constitutionality of conditions of confinement at Holmesburg.2 See Restatement (Second) of Judgments § 27 (1982).
What the Philadelphia defendants do urge, however, is that the named plaintiffs in this action and the class members whom they represent are barred by res judicata— claim preclusion — from asserting any claim which might have been asserted in the 1971 Common Pleas case. See Restatement (Second) of Judgments §§ 24, 41 (1982).
When determining the judgment preclusion effect of a judgment rendered by a state court, we are referred to the law of the rendering state. 28 U.S.C. § 1738 (1982); Migra v. Warren City School Dist. Bd. of Educ., — U.S.-, 104 S.Ct. 892, 79 L.Ed.2d 56 (1984); Allen v. McCurry, 449 U.S. 90, 101 S.Ct. 411, 66 L.Ed.2d 308 (1980). But while federal courts are directed by statute to look to state law for determination of the judgment preclusive effects of state judgments, state law itself is subject to the limitations of due process. Thus there are due process limitations upon the authority of states to attempt to bind by judgment non-participants in the underlying state lawsuit. Eisen v. Carlisle & Jacquelin, 417 U.S. 156, 176, 94 S.Ct. 2140, 2151, 40 L.Ed.2d 732 (1974); Mullane v. Central Hanover Tr. Co., 339 U.S. 306, 70 S.Ct. 652, 94 L.Ed. 865 (1950); Hansberry v. Lee, 311 U.S. 32, 61 S.Ct. 115, 85 L.Ed. 22 (1940). The position of the Philadelphia defendants is that the 1971 Common Pleas action forever bars claims for injunctive relief and damages, not only by claimants who were inmates in 1971, but also by inmates who did not become so until more than a decade later.
We need not decide whether Pennsylvania law would violate due process should it purport to go that far in applying claim preclusion. Plainly Pennsylvania law is not so extreme.
Pennsylvania applies res judicata — claim preclusion — only after a final judgment on the merits. Bearoff v. Bearoff Bros., Inc., 458 Pa. 494, 327 A.2d 72 (1974). Even after judgment, “[i]t is well settled that for the doctrine of res judicata to prevail there must be a concurrence of four conditions: 1) identity of issues, 2) identity of causes of action, 3) identity of persons and parties to the action, and 4) identity of the quality or capacity of the parties suing or sued.” Safeguard Mutual Ins. Co. v. Williams, 463 Pa. 567, 345 A.2d 664, 668 (1975). We assume arguendo, that despite the retention of jurisdiction by the Common Pleas Court, its liability determination would be'treated by Pennsylvania as a final judgment on the merits. It must nevertheless satisfy the conjunctive four factor test quoted above. That test is not satisfied by the Common Pleas Court judgment.
There is no identity of causes of action between the plaintiffs in the 1971 lawsuit and this one. No member of the present class even had a cause of action, either for injunctive relief or for damages, growing out of the conditions in Holmes-burg in 1971, for no such class member was subjected to those conditions. A Pennsylvania judgment is not conclusive on matters which by reason of the nature of the case could not have been adjudicated. E.g., Folmar v. Elliot Coal Mining Co., 441 Pa. 592, 272 A.2d 910 (1971); Salay v. Braun, 427 Pa. 480, 235 A.2d 368 (1967); Maslo Mfg. Corp. v. Proctor Elec. Co., 376 Pa. 553, 103 A.2d 743, cert. denied, 348 U.S. 822, 75 S.Ct. 36, 99 L.Ed. 648 (1954). Indeed it could not have been anticipated in *3431971 that the class members now before us would ever arrive in Holmesburg. Moreover there was no time at which notice could have been given to them so as to afford current class members an opportunity to assert the claims now claimed by the Philadelphia defendants to be barred. See Greenfield v. Villager Indus., Inc., 483 F.2d 824, 832 (3d Cir.1973); Restatement (Second) of Judgments § 42(l)(a) (1981). No steps were taken in the Common Pleas Court action to impose on any party in that action the responsibility for discharging fiduciary obligations to unknown potential future inmates. Thus there is no identity of persons or parties between the present class members and the named plaintiffs in the Common Pleas Court action. The Philadelphia defendants have not referred us to any Pennsylvania case suggesting that the Courts of the Commonwealth would apply claim preclusion, on the basis of a 1971 lawsuit, against non-parties, who could not have been notified of its pendency, so as to bar claims for injunctive relief and damages for events occurring over ten years later.
The trial court erred, therefore, in holding that res judicata — claim preclusion— bars the instant action against the Philadelphia defendants.
III.
Eleventh Amendment
The Commonwealth defendants, Waldman and Marks, contend that the action against them for either injunctive relief or damages is barred by the eleventh amendment. The claims asserted against them are predicated upon alleged violations of the Constitution. They are charged with individual acts taken under color of state law. No payments are sought from the Commonwealth Treasury. Compare Edelman v. Jordan, 415 U.S. 651, 94 S.Ct. 1347, 39 L.Ed.2d 662 (1974). No relief is sought against them under state law. Compare Pennhurst State School & Hospital v. Halderman, — U.S. -, 104 S.Ct. 900, 79 L.Ed.2d 67 (1984). They remain subject to actions for injunctive relief, Ex Parte Young, 209 U.S. 123, 28 S.Ct. 441, 52 L.Ed. 714 (1908), and to actions for money damages, except to the extent that they may enjoy official immunity.
IV.
Official Immunity
Plaintiffs claim Waldman and Marks made decisions which allegedly contributed to the unconstitutional conditions at Holmesburg. Waldman and Marks are not parties to the action in the Court of Common Pleas, but, according to plaintiffs, have been responsible in part for the failure of that court to achieve compliance with its decree. The trial court accepted their argument that the official immunity holding in Harlow v. Fitzgerald, 457 U.S. 800, 815-19, 102 S.Ct. 2727, 2737-39, 73 L.Ed.2d 306 (1981) barred the plaintiffs’ claim for monetary relief because the complaint did “not contain allegations of sufficient specificity to defeat their qualified immunity as state officials with discretionary powers.” App. 18.
The qualified immunity defense only applies, of course, to claims for money damages. The trial court correctly so assumed and relied on different grounds for dismissing the action for injunctive relief against Waldman and Marks. Initially we note that qualified immunity is an affirmative defense. There is no pleading requirement that a plaintiff must anticipate such a defense. Marks and Waldman did not move for summary judgment; thus there is no record on which to judge whether they would be able to place themselves within the doctrine of official immunity.
Judging the complaint by the standard appropriate under Rule 12(b)(6), we must assume that the plaintiffs could prove that Waldman and Marks, while knowing that the overcrowded conditions at Holmes-burg had already been adjudicated to be violations of the Constitution, took steps under color of state law which increased the inmate population and aggravated the violations. The acts complained of and the *344resulting consequences are set out quite specifically. A Rule 12(b)(6) dismissal of the complaint against Waldman and Marks for money damages, therefore, was an error of law.
V.
Abstention
As an alternative justification for dismissing the complaint the trial court relied on what it referred to as “[t]he doctrine of abstention [which] permits a federal court in its discretion to decline or postpone the exercise of its jurisdiction.” App. 14. Identifying four categories of cases in which federal courts may decline to exercise jurisdiction, the court held that three were inapplicable, but that the fourth did apply.
First, the trial court noted that under R.R. Comm’n of Texas v. Pullman Co., 312 U.S. 496, 61 S.Ct. 643, 85 L.Ed. 971 (1941) federal courts may postpone adjudication of a federal constitutional issue which may be mooted or presented in a different posture by a state court determination of a state law issue. This ground for declining to exercise jurisdiction was rejected because “there is no pertinent state law which would preclude the need to decide the constitutional issue.” App. 14. The defendants point to no potentially preclusive state law issue. Thus we agree with the district court that Pullman abstention would have been inappropriate.
Next the court considered whether the exercise of federal court jurisdiction would substantially interfere with a state regulatory scheme dealing with matters of significant importance to the state. See Burford v. Sun Oil Co., 319 U.S. 315, 63 S.Ct. 1098, 87 L.Ed. 1424 (1943); Baltimore Bank for Cooperatives v. Farmers Cheese Coop., 583 F.2d 104, 109 (3d Cir.1978). The only regulatory scheme to which the defendants could point was the decree imposed, on federal constitutional grounds, by the Court of Common Pleas. The Court rejected a Burford -type abstention, noting that “[t]he administration of the state prison system is of significant importance to the state but there are no state claims made in this case; the court action in Jackson was premised on federal not state constitutional rights.” App. 15 (footnote omitted). No special competence is claimed for the Court of Common Pleas in the administration of decrees aimed at vindicating violations of federal constitutional rights. Thus we agree that a Burford dismissal would have been inappropriate.
The court also considered whether it should decline to exercise jurisdiction on the ground that it would be called on to restrain the enforcement of a state court proceeding in which the state had a significant law enforcement interest. See Huffman v. Pursue, Ltd., 420 U.S. 592, 95 S.Ct. 1200, 43 L.Ed.2d 482 (1975); Younger v. Harris, 401 U.S. 37, 91 S.Ct. 746, 27 L.Ed.2d 669 (1971). Noting that “[t]here are no state criminal proceedings or nuisance proceedings antecedent to a criminal proceeding involved here,” App. 15, it declined to dismiss on the authority of Younger v. Harris. The trial court’s holding in this respect complies with the consistent holdings of this court that “where the pending state proceeding is a privately-initiated one, the state’s interest in that proceeding is not strong enough to merit Younger abstention, for it is no greater than its interest in any other litigation that takes place in its courts.” Williams v. Red Bank Bd. of Educ., 662 F.2d 1008, 1019 (3d Cir.1981); See Johnson v. Kelly, 583 F.2d 1242, 1249 (3d Cir.1978) (abstention improper in a challenge to constitutionality of tax sales of property when state action to quiet title was brought by private citizens); New Jersey Educ. Ass’n v. Burke, 579 F.2d 764, 767 (3d Cir.1978) (abstention improper when private plaintiffs sued state agency in state court). Since the municipal and state officials are defendants in the state proceeding resisting the enforcement of federal constitutional rights, rather than plaintiffs or prosecutors seeking vindication of state law enforcement policies, the trial court did not err in declining to dis*345miss on the authority of Younger v. Harris and its progeny.3
Finally, citing Colorado River Water Conservation District v. United States, 424 U.S. 800, 96 S.Ct. 1236, 47 L.Ed.2d 483 (1976), the trial court identified a fourth category of cases which gave it discretion to decline to exercise jurisdiction for reasons of wise judicial administration when a state court had concurrent jurisdiction over a pending action. App. 15. See also Arizona v. San Carlos Apache Tribe of Arizona, 463 U.S. 545, 103 S.Ct. 3201, 77 L.Ed.2d 837 (1983). The court concluded that, in the interest of wise judicial administration, all claims against all parties should be dismissed.
Before addressing the trial court’s treatment of Colorado River, we note the context in which the ruling was made. We must take as true the allegations of the complaint that conditions in Holmesburg, in 1982, violated the eighth and fourteenth amendments. We must take as true the allegations that a decade-old decree, which put a cap on inmate population, remains unenforced. Moreover, the litigation pending in the Court of Common Pleas is not fully parallel to that brought in the district court, for no claim for money damages was asserted in the state court case. Nor will the federal court case involve parallel litigation even over liability for injunctive relief, since the liability phase of the state court case has long since been concluded. Yet, despite that liability determination, the complaint alleges that inmates placed in Holmesburg since April 30, 1982 continue to suffer injury from ongoing violations of the eighth and fourteenth amendments.
The basic rule has always been that the pendency of a state court proceeding is not a reason for a federal court to decline to exercise jurisdiction established by Congress. McClellan v. Carland, 217 U.S. 268, 281-82, 30 S.Ct. 501, 504, 54 L.Ed. 762 (1910). Moreover a state court having jurisdiction over a class action may not enjoin a parallel class action in a federal court. Donovan v. City of Dallas, 377 U.S. 408, 84 S.Ct. 1579, 12 L.Ed.2d 409 (1964). These holdings recognize the deference which federal courts owe to the legislative determination by Congress that plaintiffs have been given a choice of forums. See Meredith v. Winter Haven, 320 U.S. 228, 236, 64 S.Ct. 7, 11, 88 L.Ed. 9 (1943).
The Supreme Court has recognized a narrow exception to the basic rule, where it has been able to identify, in other Congressional legislation, a tempering of the policy of enforcing the plaintiff’s choice of a federal forum in favor of a policy of avoiding . duplicative and inconvenient litigation. In Colorado River Water Conservation District v. United States, supra, the Court found such a modification in the McCarren Amendment, c. 651, Title II, § 208(a)-(c), 66 Stat. 560 (1952) (codified as 43 U.S.C. § 666 (1982)), in which Congress consented to suit in state courts against the United States when the United States was asserting claims for water rights under a state water rights scheme. The Court held that, in light of the McCarren amendments, deference to a parallel state proceeding was appropriate, since such deference would a) provide a single court with exclusive jurisdiction over interdependent water rights, b) avoid piecemeal litigation, and e) provide for resort to a more convenient forum, one which had first assumed jurisdiction. Even while announcing this narrow parallel litigation exception to the basic rule, however, the Court took pains to note “the virtually unflagging obligation of the federal courts to exercise the jurisdiction given them.” Id. 424 U.S. at 817, 96 S.Ct. at 1246, citing England v. Medical Examiners, 375 U.S. 411, 415, 84 S.Ct. 461, 464, 11 L.Ed.2d 440 (1964). Under Colorado River a district court may dismiss only upon “a carefully *346considered judgment” which “[ojnly the clearest of justifications will warrant----” 424 U.S. at 818-19, 96 S.Ct. at 1246-47.
The teaching of the Colorado River case is that only “exceptional” circumstances will permit a federal court to refrain from exercising its jurisdiction for reasons of wise judicial administration due to the presence of a concurrent state court proceeding.
17 C. Wright, A. Miller & E. Cooper, Federal Practice and Procedure § 4247 (1978) p. 519.
Recently the Supreme Court has reconfirmed that the parallel litigation exception to the basic rule of McClellan v. Carland is a narrow one requiring the clearest justification. In Moses H. Cone Memorial Hospital v. Mercury Construction Corporation, 460 U.S. 1, 103 S.Ct. 927, 74 L.Ed.2d 765 (1983), the Court held that a diversity action to compel arbitration should not have been dismissed in favor of a state court declaratory judgment action in which the federal plaintiff was a defendant. There was no assumption by the state court of control over a res or property, and no contention that the federal forum was less convenient to the litigants. Id. at 939. Moreover “avoidance of piecemeal litigation, and the order in which jurisdiction was obtained by the concurrent forums — far from supporting the stay, actually counsel against it.” Id. Addressing a factor not considered in Colorado River, the Court held that the existence of a federal law rule of decision, which either court must apply, was a major reason for exercising federal jurisdiction. Justice Brennan wrote:
[w]e emphasize that our task in cases such as this is not to find some substantial reason for the exercise of federal jurisdiction by the district court; rather, the task is to ascertain whether there exist “exceptional” circumstances, the “clearest of justifications,” that can suffice under Colorado River to justify the surrender of that jurisdiction. Although in some rare circumstances the presence of state-law issues may weigh in favor of that surrender, ... the presence of federal-law issues must always be a major consideration weighing against surrender.
103 S.Ct. at 942.
The test for application of the parallel litigation exception set forth in Colorado River and reiterated in Moses H. Cone cannot be satisfied in this instance. The cases are not truly parallel since the federal court plaintiffs seek money damages while the state court plaintiffs did not. The liability phase of the state court case is long concluded, and thus parallel litigation on liability even for injunctive relief is not an issue. Indeed the plaintiffs may be able to avoid some steps in the federal court proceeding by offensive collateral estoppel use of the state court judgment. The state court is not a more convenient forum since both courts are located in the same city, equally accessible to Holmesburg. No federal statute suggests a congressional policy tempering in any way the basic policy of affording plaintiffs a choice of forum. Finally, of special significance in light of Moses H. Cone, the law applied in either forum is federal law. The mere pendency of a state court injunction predicated on federal law, which according to the complaint has not produced an alleviation of ongoing violations of the constitution, is not such an exceptional circumstance as to relieve the federal courts of “the .virtually unflagging obligation ... to exercise the jurisdiction given them.” 424 U.S. at 817, 96 S.Ct. at 1246. Thus we cannot affirm the dismissal of the complaint on the ground relied on by the trial court.
VI.
Conclusion
The judgment dismissing the complaint on the defendants’ Rule 12(b)(6) motion will be reversed, and the case remanded for further proceedings.
. Defendant Marks moved to dismiss for the following reasons:
1. Plaintiffs’ Amended Complaint fails to state a claim against defendant Marks upon which relief can be granted.
2. Plaintiffs’ action against defendant Marks is barred by the eleventh amendment.
3. The claims for injunctive relief by plaintiffs who are no longer confined to Holmes-burg are moot.
4. Plaintiffs' action is barred by principles of res judicata and collateral estoppel.
5. Defendant Marks is immune from liability for money damages.
Defendant Waldman moved to dismiss for the following reasons:
1. The amended complaint fails to state a claim against defendant Waldman upon which relief can be granted because of lack of specificity.
2. The action against defendant Waldman is barred by the eleventh amendment to the United States Constitution.
3. The action is barred by principles of res judicata and collateral estoppel.
The Philadelphia defendants also moved to dismiss, but the specific reasons relied upon do not appear in the record before us.
Grounds for dismissal other than those specified in the written motions apparently were addressed at oral argument in the trial court. The record contains no transcript of that argument. Thus we must depend on the trial court’s opinion to determine what contentions were made in support of the Rule 12(b)(6) motions.
. The plaintiffs plead that they are entitled to rely upon the decree in the Common Pleas action. Amended Complaint, 50, App. 36.
. The defendants do not contend that the plaintiffs have failed to exhaust state administrative remedies for prisoner grievances which have been approved by the Attorney General pursuant to the Civil Rights of Institutionalized Persons Act. Pub.L. No. 96-247, § 2, 94 Stat. 349 (1980) (codified at 42 U.S.C. § 1997e(a)(l) (1982)). So far as the record discloses, Pennsylvania has not obtained approval for any such remedies.