concurring in part and dissenting in part.
I agree with Judge Posner that this suit should be dismissed under the doctrine of res judicata, but I arrive at this position through a different analysis. Judge Posner fits his result into the existing strictures of res judicata doctrine by finding that the plaintiffs could have brought their entire cause of action in one court. I would hold instead that in finding this suit barred by res judicata, it is unnecessary to find that the plaintiffs could have brought all their claims in one court, as long as they could have brought all their claims contemporaneously in different courts. We should treat this matter as we would any other case in which the plaintiff litigates a dispute under one theory, loses, and then brings a second suit to litigate the same dispute under a different theory.1 In such a situation, absent equitable circumstances not present here, fairness to a defendant requires that the second suit be barred by res judicata.
The basic principles of res judicata were stated recently by this court in the case of Mandarino v. Pollard, 718 F.2d 845 (7th Cir.1983):
“The doctrine of res judicata is that a final judgment on the merits in a court of competent jurisdiction bars the same parties or their privies from relitigating not only the issues which were in fact raised and decided but also all other issues which could have been raised in the prior action.... The essential elements of the doctrine are generally stated to be: (1) a final judgment on the merits in an earlier action; (2) an identity of the cause of action in both the earlier and the later suit; and (3) an identity of parties or their privies in the two suits.”
At 849 (quoting Lee v. City of Peoria, 685 F.2d 196,199 (7th Cir.1982)). In the present case, the res judicata controversy revolves around whether there is an identity of the cause of action and whether the issues in the present suit should and could have been raised earlier.
As a threshold matter, there is a question about which body of res judicata law should be applied here. As Judge Cudahy points out, there is language in the Supreme Court case of Kremer v. Chemical Construction Corp., 456 U.S. 461, 102 S.Ct. 1883, 72 L.Ed.2d 262 (1982), that suggests that when a federal court determines the preclusive effect of an earlier state judgment, it always must follow the res judicata rules of the state from which the judgment is taken. (“It has long been established that § 1738 does not allow federal courts to employ their own rules of res judicata in determining the effect of state judgments.” Id. at 481-82, 102 S.Ct. at 1897-98.) However, the Supreme Court in Kremer did not hold that a federal court may not give a state court judgment greater preclusive effect than the courts of that state would give it.2 *1164As Judge Posner notes, there is no reason for such a holding. In Kremer itself, the Court stated that Congress’s purpose in enacting section 1738 was “specifically to insure that federal courts ... would be bound by state judgments.” Id. at 484 n. 24, 102 S.Ct. at 1889 n. 24. See also Davis v. Davis, 305 U.S. 32, 40, 59 S.Ct. 3, 6, 83 L.Ed. 26 (1938). The requirement that the federal courts give the same credit to state court judgments as would the courts of that state thus can be interpreted as a convenient means to ensure that state judgments are given full credit; it is not an end in itself. Therefore, I agree with Judge Posner that we are not constrained by section 1738 as long as we do not give a state court judgment less preclu-sive effect than would the courts of the state from which the judgment is taken.
Though we are not bound by Illinois law, the Illinois courts have stated traditional res judicata principles that are applicable to the facts of this case. Under Illinois law, a cause of action for purposes of res judicata is defined as follows:
[A] cause of action consists of a single core of operative facts which give the plaintiff a right to seek redress for the wrong concerned. Even though one group of facts may give rise to different claims for relief upon different theories of recovery, there remains a single cause of action.
Morris v. Union Oil Co. of California, 96 Ill.App.3d 148, 157, 51 Ill.Dec. 770, 777, 421 N.E.2d 278, 285 (1981), quoted in Lee v. City of Peoria, 685 F.2d at 200. See also Gasbarra v. Park-Ohio Industries, 655 F.2d 119,121 (7th Cir.1981) (courts have sought to discover “whether the entire amount claimed to be due plaintiff arises out of one and the same act or contract”) (quoting Freeman & Co. v. Regan Co., 332 Ill.App. 637, 645, 76 N.E.2d 514, 517-18 (1947)). The Illinois courts also have stated that plaintiffs are required to set out in their pleadings all grounds for recovery that they may have. They may not maintain a subsequent suit after the loss of an earlier one based upon the same facts by the simple expediency of limiting the theories of recovery advanced in the pleadings of the first. Baird & Warner v. Addison Industrial Park, 70 Ill. App.3d 59, 64, 26 Ill.Dec. 1, 7, 387 N.E.2d 831, 837 (1979); Prochotsky v. Union Central Life Insurance, 2 Ill.App.3d 354, 356, 276 N.E.2d 388, 390 (1971). These rules are founded upon “the plainest and most substantial justice, that litigation should have an end and that no person should be unnecessarily harassed with a multiplicity of suits.” Baird & Warner v. Addison Industrial Park, 70 Ill.App.3d at 64, 26 Ill.Dec. at 7, 387 N.E.2d at 837. See also Dorland v. Steinbrecher, 50 Ill.App.2d 344, 347, 200 N.E.2d 424, 425 (1964).
As a matter of federal law, the plaintiffs’ earlier state court suits and their current federal suit should be considered to involve the same cause of action for purposes of res judicata. In each suit, the plaintiffs essentially were challenging the legality of the defendant’s admissions procedures. In the state suits, their position was based on the theory that the procedures were in violation of state common law and due process. In their federal suit, they have claimed that the procedures amount to a group boycott, in violation of federal antitrust law. .The state and federal suits revolve around the same set of operative facts: the facts relating to the manner in which the defendant has chosen to limit its membership. In short, the suits are so closely related that logic dictates that the principles of res judi-cata should be applied to them.
This pragmatic approach to identifying a cause of action has significant support in both the law and legal literature. The Restatement (Second) of Judgments, which uses the terms “cause of action” and “claim” interchangeably, states:
[T]he concept of a transaction ... connotes a natural grouping or common nucleus of operative facts. Among the factors relevant to a determination whether the facts are so woven together as to constitute a single claim are their relatedness in time, space, origin, or motivation, and whether, taken together, they form a convenient unit for trial purposes.
*1165The present trend is to see claim in factual terms and to make it coterminous with the transaction regardless of the number of substantive theories, or variant forms of relief flowing from those theories, that may be available to the plaintiff; regardless of the number of primary rights that may have been invaded; and regardless of the variations in the evidence needed to support the theories or rights.3
Restatement (Second) of Judgments § 24 comments a and b (1980). Professor Currie, cited by Judge Posner, has also suggested a pragmatic approach to the application of res judicata, one in which the “cause of action” terminology would be unnecessary: “Perhaps the time has come ... to ask simply whether the party to be precluded had adequate opportunity to litigate the matter in the earlier proceeding and whether the matter is closely enough related to the original controversy so that judicial economy would be served by confining litigation to one proceeding.” Currie, Res Ju-dicata: The Neglected Defense, 45 U.Chi.L. Rev. 317, 342 (1978).4 Finally, and most importantly, it should be noted that this circuit has previously adopted a pragmatic approach to determining what constitutes a cause of action. See Himel v. Continental Illinois National Bank, 596 F.2d 205, 209 (7th Cir.1979) (“primary test for determining if two suits are premised on the same cause of action is whether both suits arise under the same factual situation”), quoted in Gasbarra v. Park-Ohio, Inc., 655 F.2d at 121. See also Lambert v. Conrad, 536 F.2d 1183, 1186 (7th Cir.1976) (“[sjince both suits pertain to the same disputed facts and arise out of the same operative facts, they clearly are the same cause of action”).
Having determined that the suits at issue here involved identical causes of action for purposes of the res judicata doctrine, the question now, becomes whether the substance of the present suit could have been raised earlier. A basic tenet of the res judicata doctrine is that a party may not litigate a dispute and then, upon an unsuccessful disposition, revive the same cause of action with a new theory. This principle has been stated repeatedly by this and other circuits. See, e.g., Mandarino v. Pollard, 718 F.2d 845 at 849 (7th Cir.1983); Harper Plastics, Inc. v. Amoco Chemicals Corp., 657 F.2d 939, 945 (7th Cir.1981); Roach v. Teamsters Local Union No. 688, 595 F.2d 446, 450 (8th Cir.1979); Astron Industrial Associates v. Chrysler Motors, 405 F.2d 958, 961-62 (5th Cir.1968); Grace v. Grace, 394 F.2d 127, 128 (2d Cir.1968); Brotherhood of Railroad Trainmen v. Chicago, Milwaukee, St. Paul & Pacific Railroad, 380 F.2d 605, 608 (D.C.Cir.1967).5 The instance where a party does attempt to revive an unsuccessful cause of action with a new theory is a particularly compelling case for the application of res judicata principles because it is almost always avoidable and can involve significant inconvenience to a defendant. One of the primary purposes of the res judicata doctrine is to protect defendants from the expense and vexation attending multiple lawsuits. Montana v. United *1166States, 440 U.S. 147, 153, 99 S.Ct. 970, 973, 59 L.Ed.2d 210 (1979); Mandarino v. Pollard, at 848. When a defendant is charged with wrongdoing, expends considerable resources to defend him or herself in court, and is awarded a final judgment, it is unfair to make that defendant then go through the whole process anew to defend the same actions that were attacked in the first suit. Yet this is a description of what the plaintiffs would have us sanction in this case.
If this is not a classic case of losing and trying again on a different theory, it is only because, as Judge Cudahy argues, the plaintiffs could not have brought their federal antitrust claim in state court. I agree with Judge Cudahy that this jurisdictional obstacle excuses the plaintiffs from bringing their federal claim in state court with their state claims, but it cannot excuse their waiting until their state suits were lost — a period of more than three years — before bringing their federal action. Insofar as the jurisdictional competency rule relied on by Judge Cudahy requires only that plaintiffs raise those theories of recovery available to them in a particular court — a court of their own choosing — and allows them to raise other theories at any other time, it is a technical rule that is not well designed to serve the policies behind the doctrine of res judicata. I suggest that it is a better rule to require plaintiffs who are unable to bring their entire cause of action in the forum of their choice, such as the plaintiffs in this case, at least to bring their entire cause of action relatively contemporaneously, in order to avoid their having two successive “bites of the apple” at the expense of the defendant. In some cases plaintiffs may choose to bring their entire cause of action in federal court and attempt to have their state claims adjudicated under that court’s pendent jurisdiction. In other cases plaintiffs may choose to split their cause of action between state and federal courts. Either course would be preferable to what the plaintiffs chose to do in the present case.
I do not suggest that requiring plaintiffs to bring their entire cause of action within a reasonable period of time would necessarily advance the interests of judicial economy, though I am satisfied that such a requirement would not increase the total volume of litigation.6 This equitable requirement is simply one that is fair to defendants and at the same time poses no undue hardship on plaintiffs.7 While this position represents an extension of the more confined and dated interpretations of res judi-*1167cata,8 it is in greater compliance with the spirit of the res judicata doctrine than are the more rote approaches. As the Supreme Court has stated, “[T]he doctrine of res judicata is not a mere matter of practice or procedure inherited from a more technical time than ours. It is a rule of fundamental and substantial justice, ‘of public policy and private peace,’ which should be cordially regarded and enforced by the courts.... ” Federal Department Stores v. Moitie, 452 U.S. 394, 401, 101 S.Ct. 2424, 2429, 69 L.Ed.2d 103 (1981) (quoting Hart Steel Co. v. Railroad Supply Co., 244 U.S. 294, 299, 37 S.Ct. 506, 508, 61 L.Ed. 1148 (1917)). In this case, because the plaintiffs had an opportunity to litigate their federal antitrust claim in a court of competent jurisdiction and failed to do so until their other legal theories failed, they now should be equitably barred from bringing a federal antitrust suit.9
Because I find the plaintiffs’ suit barred by res judicata, I deem it unnecessary and inappropriate to reach the discovery question raised in this case. It is essential, however, that the contempt issue be addressed. On that question, I agree with Judge Wood that the contempt citation should remain intact apart from the fact that the plaintiffs’ suit has been barred by res judicata, and I join that portion of Judge Wood’s opinion dealing with the viability of the contempt citation.
. Although Dr. Marrese’s state court suit was not actually dismissed until after his federal suit was filed, it appears from the record before us that it was effectively defunct before his federal suit was filed. Once Dr. Treister’s suit went to the Illinois Appellate Court on appeal, Dr. Marrese’s suit, which raised identical issues, was stayed by the circuit court pending Dr. Treister’s appeal. The Illinois Appellate Court affirmed the dismissal of Dr. Treister’s complaint for failure to state a cause of action in October of 1979, and shortly thereafter the Illinois Supreme Court denied Dr. Treister’s petition for leave to appeal. Following this denial, on March 21, 1980, both Dr. Marrese and Dr. Treister filed this action in federal court. I find nothing in the record indicating the reason that Dr. Marrese’s suit was not dismissed following the dismissal of Dr. Treister’s identical suit. In the absence of contrary evidence, there is a compelling inference that Dr. Marrese expected that his state suit would be dismissed at the time he filed his federal suit.
. In Kremer, the Court stated: “Congress has specifically required all federal courts to give preclusive effect to state-court judgments whenever the courts of the State from which the judgments emerged would do so.” Kremer v. Chemical Construction Corp., 456 U.S. at 482, 102 S.Ct. at 1898 (quoting Allen v. McCurry, 449 U.S. 90, 96, 101 S.Ct. 411, 415, 66 L.Ed.2d 308 (1980)). However, the Court did not state that federal courts must refuse to give preclusive effect to state-court judgments when the courts of the state from which the judgments emerged would so refuse.
. As Judge Cudahy notes, there is some authority in Illinois law for a similarity of evidence test to determine identity of causes of action. However, Illinois courts have explicitly stated that this is only one test that can be employed for this purpose. See LaGrange Federal Savings and Loan Association v. Rock River Corp., 97 Ill.App.3d 712, 715, 53 Ill.Dec. 112, 115, 423 N.E.2d 496, 500 (1981); Rotogravure Service, Inc. v. R.W. Borrowdale Co., 77 Ill.App.3d 518, 525, 32 Ill.Dec. 762, 769, 395 N.E.2d 1143, 1148 (1978).
. Professor Currie is correct in suggesting that the sometimes overly technical inquiry into whether two suits involve the same cause of action can obfuscate the more fundamental inquiry for purposes of res judicata: whether the suits are related in such a way that a final determination in one should bar litigation of the other.
. This principle also has been stated as follows: Having been defeated on the merits in one action, a plaintiff sometimes attempts another action seeking the same or approximately the same relief but adducing a different substantive law premise or ground. This does not constitute the presentation of a new claim when the new premise or ground is related to the same transaction or series of transactions, and accordingly the second action should be held barred.
Restatement (Second) of Judgments, § 25 comment d.
. Of course, the requirement that is proposed may appear to be inefficient in a particular case where a plaintiff brings two contemporaneous suits and only one proves to be necessary to win a judgment. However, the same observation can be made about the res judicata doctrine generally, since it requires plaintiffs to present all possible theories of recovery when they may not all be necessary. That the res judicata doctrine is thought to promote judicial economy, see Montana v. United States, 440 U.S. 147, 153, 99 S.Ct. 970, 973, 59 L.Ed.2d 210 (1979), reflects the belief that in the long rim it is more efficient to consolidate closely-related matters at an early stage rather than run the risk of litigating each one separately over a long period of time. This belief seems equally relevant to the situation in the instant case. Moreover, requiring plaintiffs to bring their entire cause of action at approximately the same time would seem to promote judicial economy insofar as it creates some incentive for plaintiffs in cases such as this to bring their entire cause of action in federal court. In addition, to the extent that some plaintiffs still may wish to split their cause of action, requiring them to split it contemporaneously rather than successively allows for some flexibility at the trial level that may reduce the amount of unnecessary litigation. For example, under certain circumstances an Illinois trial judge may dismiss a suit if there is another action between the same parties for the same cause pending in a different court, including a federal court. See 2-619(a)(3) of the Illinois Code of Civil Procedure (Ill.Rev.Stat., 1982, ch. 110, par. 2-619(a)(3)); Skolnick v. Martin, 32 Ill.2d 55, 203 N.E.2d 428 (1964). Similarly, in some situations the federal court may see fit to stay its proceedings under a doctrine of abstention. See 17 Wright, Miller & Cooper, Federal Practice and Procedure: Jurisdiction §§ 4241-4248 (1978).
. I recognize that a plaintiff may have theories of recovery under state law that are less complex than his or her exclusively federal theories. In such a situation, a plaintiff may still proceed in federal court. Pendent jurisdiction could allow the plaintiff to litigate one or more of the state claims before others if a district judge is satisfied that such priority should be given.
. It is worth emphasizing that this interpretation of the res judicata doctrine is limited to those cases in which one or more of the plaintiffs grounds for recovery can be litigated only in federal court, such as cases involving the federal antitrust laws. Where no such jurisdictional obstacle exists, it is already well settled that the plaintiffs entire cause of action must be brought contemporaneously, and in one court. See Restatement (Second) of Judgments, § 25.
. Although the fact that a plaintiff has actually lost an earlier suit involving the same cause of action should ordinarily be sufficient reason to invoke the res judicata doctrine, it is not essential that this occur. For purposes of applying res judicata, it may well be enough that a plaintiff has waited until the early stages of litigation are over in one suit before bringing the other, or that an unreasonable period of time has passed between the filing of the first and second suits. The reasonableness of the plaintiffs actions in a particular case should be a matter left to the sound discretion of the trial court that is being asked to bar the second suit on the basis of the res judicata doctrine.