dissenting in part.
While I am in general agreement with the phases of this case touched on by the Court, I add a few words because its opinion does not fully explore the issues which will be dispositive of this case on remand to the District Court.
Federal Rule Civ. Proc. 23 (c) (4) provides: “When appropriate (A) an action may be brought or maintained as a class action with respect to particular issues, or (B) a class may be divided into subclasses and each subclass treated as a class, and the provisions of this rule shall then be construed and applied accordingly.”
*180As Judge Oakes, speaking for himself and Judge Timbers, said below:
“The plaintiff class might, for example, be divided into much smaller subclasses ... of odd lot buyers for particular periods, and one subclass treated as a test case, with the other subclasses held in abeyance. Individual notice at what would probably be a reasonable cost could then be given to all members of the particular small subclass who can be easily identified.” 479 F. 2d 1005, 1023 (dissenting from denial of rehearing en banc).
Or a subclass might include those on monthly investment plans, or payroll deduction plans run by brokerage houses.1 The possibilities, though not infinite, are numerous.
*181The power to create a subclass is clear and unambiguous. Who should be included and how large it should be are questions that only the District Court should resolve. Notice to each member of the subclass would be essential under Rule 23 (c) (2); and under Rule 23 (c) (2) (A) any notified member may opt out.. There would remain the question whether the subclass suit is manageable. But since the subclass could be chosen in light of the non-manageability of the size of the class whose claims are presently before us, there is no apparent difficulty in that sense.
The statute of limitations, it is argued, has run or is about to run on many of these classes. We held in American Pipe & Construction Co. v. Utah, 414 U. S. 538, that the start of a class action prior to the running of the statute protects all members of the class. Whether that rule should obtain for the benefit of other members who could have been included in the subclass bringing suit, but for the manageability issue, is a question we have not decided.2 Moreover, if the subclass sues and wins or *182sues and loses, questions covering the rights of members of the larger class who are not parties would be raised. These are questions we have not answered.3 But the fact that unresolved questions of law would remain is not an insurmountable obstacle, and Rule 23 (c) (4) (B) expressly authorizes subclasses to sue in lieu of a full class. Rule 23 (c)(4)(B) may have had, as a forerunner, the proposal stated by Judge Weinstein in 1960:
“When there is a question of law or fact common to persons of a numerous class whose joinder is impracticable, one or more of them whose claims or defenses are representative of the claims or defenses of all and who will fairly and adequately protect the interests of all may sue or be sued on behalf of all.” 4
In explanation he added:
“Such a rule would provide six requirements for a class action: (1) a class, (2) numerous members, *183(3) common question of law or fact, (4) impracticability of joinder, (5) representative claim or defense, (6) fair and adequate protection of absentees.
“Almost any 'bond of association’ in an event or status out of which a legal dispute arose is sufficient to constitute a class. The class must be numerous but need not be so large that, in itself, this factor makes it impracticable to bring them all before the court. A number of members sufficient to satisfy present Section 195 [of the New York Civil Practice Act] would satisfy the proposed rule. Size, modesty of monetary interest, inability to locate members and difficulty of obtaining jurisdiction should all be considered in determining impracticability of joinder.” 5
The Court permits Eisen to redefine his class either by amending his complaint pursuant to Fed. Rule Civ. Proc. 15, or by proceeding under Rule 23 (c) (4). While Eisen may of course proceed by amending his complaint to define a subclass, it is clear that he need not do so.6 Definition of the subclass would properly be accomplished by order of the District Court, as permitted by Rules 23 (c)(4) and 23 (c)(1), without amendment of the complaint as filed. While the complaint alleges that *184Eisen sues on his behalf and on behalf of all purchasers and sellers of odd lots, it adds, “Plaintiff will fairly insure the adequate representation of all such persons.” Problems of manageability covered by Rule 23 (b) (3) (D) arise only after issues are joined and the District Court is engaged in shaping up the litigation for a trial on the merits. If it finds that a subclass would be more appropriate, no new action need be started nor any amended complaint filed.
Rule 23 (c)(1) provides: “As soon as practicable after the commencement of an action brought as a class action, the court shall determine by order whether it is to be so maintained. An order under this subdivision may be conditional, and may be altered or amended before the decision on the merits.”
It is as plain as words can make it that the court which decides that a full class action can be maintained can alter or amend its order “before the decision on the merits.” One permissible way in which the court’s order may be changed is to have it “altered” as provided in Rule 23 (c)(1) by reducing the larger class to a subclass as provided in the same subsection — Rule 23 (c) (4)(B). The prerequisites of a class cause of action are described in Rule 23 (a). In the instant case that hurdle has been passed and we are at the stage of notice requirements and manageability. Not an iota of change is made in the cause of action by restricting it to a subclass.
The purpose of Rule 23 is to provide flexibility in the management of class actions, with the trial court taking an active role in the conduct of the litigation. See Dolgow v. Anderson, 43 F. R. D. 472, 481-482 (EDNY); Green v. Wolf Corp., 406 F. 2d 291, 298 (CA2), cert. denied, 395 U. S. 977. Lower federal courts have recognized their discretion to define those subclasses proper to prosecute an action without being bound by the plaintiff’s *185complaint. See, e. g., Dolgow v. Anderson, supra, at 491-493; Philadelphia Elec. Co. v. Anaconda American Brass Co., 43 F. R. D. 452, 462-463 (ED Pa.). See generally 7A C. Wright & A. Miller, Federal Practice and Procedure § 1790, p. 187; 3B J. Moore, Federal Practice ¶ 23.65. And, as Rule 23 (c)(1) clearly indicates, the courts retain both the power and the duty to realign classes during the conduct of an action when appropriate. See, e. g., Carr v. Conoco Plastics, Inc., 423 F. 2d 57, 58 (CA5), cert. denied, 400 U. S. 951; Johnson v. ITT-Thompson Industries, Inc., 323 F. Supp. 1258, 1262 (ND Miss.); Ostapowicz v. Johnson Bronze Co., 54 F. R. D. 465, 466 (WD Pa.); Baxter v. Savannah Sugar Refining Corp., 46 F. R. D. 56, 60 (SD Ga.). That discretion can be fully retained only if the full-class complaint is preserved when a subclass is defined to prosecute the action. The bounds of the subclass can then be narrowed or widened by order of the District Court as provided in Rule 23 (c)(1), without need to amend the complaint and without the constraints which might exist if the complaint had earlier been amended pursuant to Rule 15 to include only the subclass.
I agree with Professor Chafee that a class action serves not only the convenience of the parties but also prompt, efficient judicial administration.7 I think in our society that is growing in complexity there are bound to be innumerable people in common disasters, calamities, or ventures who would go begging for justice without the class action but who could with all regard to due process be protected by it. Some of these are consumers whose claims may seem de minimis but who alone have no practical recourse for either remuneration or injunctive relief, Some may be environmentalists who have no photographic development plant about to be ruined because of *186air pollution by radiation but who suffer perceptibly by smoke, noxious gases, or radiation. Or the unnamed individual may be only a ratepayer being excessively charged by a utility, or a homeowner whose assessment is slowly rising beyond his ability to pay.
The class action is one of the few legal remedies the small claimant has against those who command the status quo.8 I would strengthen his hand with the view of creating a system of law that dispenses justice to the lowly as well as to those liberally endowed with power and wealth.
The parties and courts below concentrated on whether a class action could be sustained on behalf of all six million odd-lot investors, so that the record is limited in information bearing on what manageable subclasses could be created.
There is, nonetheless, indication that certain subclasses might be economically manageable. Counsel for respondent Carlisle & Jac-quelin stated in oral argument before the Court of Appeals that 100,000 shareholders participate in his client’s Monthly Investment Plan, and that Carlisle & Jacquelin corresponds with those investors. Merrill Lynch corresponds with 150,000 people participating in a payroll deduction investment plan. Whether Eisen or any other plaintiff who may come forward to intervene fits in such a subclass, we do not know. But if brokerage houses correspond regularly in the course of business with such odd-lot investors, the marginal cost of providing the individual notice required by Rule 23 (c) (2) might be nothing more than printing and stuffing an additional sheet of paper in correspondence already being sent to the investor, or perhaps only programing a computer to type an additional paragraph at the bottom of monthly or quarterly statements regularly mailed by the brokers.
A subclass of those who had engaged in numerous transactions might also be defined, so that the recovery per class member might be large enough to justifiy the cost of notice and management of the *181action. A survey of only four of 14 wire firms revealed 2,000 customers with 10 or more transactions between 1962 and 1966. 52 F. R. D. 253, 259, 267, and n. 10.
By defining more definite subclasses such as those discussed, moreover, the problems inherent in distributing an eventual judgment would be reduced. Class members would be more readily identifiable, with more readily accessible transaction records and individually provable damages.
In this case, the entire class was defined in the original complaint, and the defendants were put on notice within the period of limitation of their potential liability, serving the purpose of the statute of limitations even if the substantive merits were eventually to be prosecuted in the form of a subclass action with the class action held in abeyance. “Within the period set by the statute of limitations, the defendants have the essential information necessary to determine both the subject matter and size of the prospective litigation, whether the actual trial is conducted in the form of a class action, as a joint suit, or as a principal suit with additional inter-*182venors.” American Pipe & Construction Co. v. Utah, 414 U. S. 538, 555. And see Wheaton, Representative Suits Involving Numerous Litigants, 19 Cornell L. Q. 399, 423 (1934).
If the subclass lost, it is argued that other investors not members of that subclass could not be precluded from prosecuting successful suits of their own, since they had never had their day in court or necessarily even been apprised of the subclass action. See Hansberry v. Lee, 311 U. S. 32; F. James, Civil Procedure § 11.26 (1965); IB J. Moore, Federal Practice ¶ 0.411 [ 1] (1974). If the subclass won, strict application of the doctrine of mutuality of estoppel would limit the usefulness of that subclass victory in suits brought by investors not members of that subclass. See generally F. James, supra, §11.31; IB J. Moore, supra, ¶ 0.412 [1] (and Supp. 1973), and cases cited therein. And see Vestal, Preclusion/Res Judicata Variables: Parties, 50 Iowa L. Rev. 27, 55-59 (1964); Note, 35 Geo. Wash. L. Rev. 1010 (1967); Currie, Mutuality of Collateral Estoppel: Limits of the Bernhard Doctrine, 9 Stan. L. Rev. 281 (1957).
Weinstein, Revision of Procedure: Some Problems in Class Actions, 9 Buffalo L. Rev. 433, 458.
Id., at 458-459 (footnotes omitted).
Were Eisen to be remitted to an individual action, as he would be if he refused to pay the cost of notice even to a subclass, amendment of the complaint might be called for by the District Court. Under Rule 23 (d)(4), the District Court may in some instances require that pleadings be amended to eliminate class allegations. The Advisory Committee Notes indicate that this provision is to be applied only when a suit must proceed as a nonclass, individual action, not when, as here, an appropriate class exists and the action must be prosecuted in the first instance by a subclass only because of problems of manageability. See 28 U. S. C. App., p. 7767.
Z. Chafee, Some Problems of Equity 149 (1950).
Judge Weinstein writing in the N. Y. Law Journal, May 2, 1972, p. 4, col. 3, said:
“Where, however, public authorities are remiss in performance of this responsibility for reason of inadequate legal authority, excessive workloads or simple indifference, class actions may provide a necessary temporary measure until desirable corrections have occurred. The existence of class action litigation may also play a substantial role in bringing about more efficient administrative enforcement and in inducing legislative action.
“The matter touches on the issue of the credibility of our judicial system. Either we are committed to make reasonable efforts to provide a forum for adjudication of disputes involving all our citizens — including those deprived of human rights, consumers who overpay for products because of antitrust violations and investors who are victimized by insider trading or misleading information— or we are not. There are those who will not ignore the irony of courts ready to imprison a man who steals some goods in interstate commerce while unwilling to grant a civil remedy against the corporation which has benefited, to the extent of many millions of dollars, from collusive, illegal pricing of its goods to the public.
“When the organization of a modern society, such as ours, affords the possibility of illegal behavior accompanied by widespread, diffuse consequences, some procedural means must exist to remedy — or at least to deter — that conduct.”