of various environmental statutes allowed intervention as of right in these circumstances. Alternatively, CNA claimed that it should be allowed to intervene by permission pursuant to Rule 24(b).

The District Court denied the request to intervene as of right, but granted CNA's application to become a permissive intervenor. The court concluded, however, that CNA's right to participate should be subject to three conditions. First, it held that CNA could not assert any claim for relief that had not already been requested by one of the original parties. The court found that "allowing applicants to assert their individualized damage and other claims would burden and expand an already complex litigation, and could jeopardize the possibility of settlement." App. to Pet. for Cert. A-19. Second, CNA could not intervene in the Government plaintiffs' claim for recovery of the clean-up costs. Finally, in an effort to "minimize any delay and confusion involved in discovery," the District Court ruled that CNA could not file any motions or conduct its own discovery unless it first conferred with all the original parties, and then obtained permission to go forward from at least one of these litigants. Id., at A-20. The court emphasized, though, that CNA had the right to attend all depositions, to participate to the extent not duplicative of the original parties, and to receive copies of all discovery material produced by the other litigants.

...

"(b) PERMISSIVE INTERVENTION. Upon timely application anyone may be permitted to intervene in an action: . . . (2) when an applicant's claim or defense and the main action have a question of law or fact in common. In exercising its discretion the court shall consider whether the intervention will unduly delay or prejudice the adjudication of the rights of the original parties."

'CNA alleged that it had the right to intervene under the Safe Drinking Water Act, 88 Stat. 1690, as amended, 42 U. S. C. § 300j-8, the Resource Conservation and Recovery Act, 90 Stat. 2825, as amended, 42 U. S. C.

§ 6972 (1982 ed. and Supp. III), and the Clean Water Act, as added, 86 Stat. 888, 33 U. S. C. § 1365.

CNA filed an immediate appeal, protesting both the denial of the application to intervene as of right and the restrictions imposed on permissive intervention. The Court of Appeals for the Ninth Circuit initially dismissed the appeal, finding that the District Court order was not a "final decision" within the meaning of 28 U. S. C. § 1291. The court's decision was largely based on the fact that CNA had been made a party to the litigation and could protect its interests fully during an appeal from the final judgment. The Ninth Circuit also noted that its decision was consistent with the results reached by other Courts of Appeals in similar cases. The court subsequently withdrew its opinion, however, concluding that the holding was inconsistent with Ninth Circuit precedent. Relying on California v. Block, 690 F. 2d 753, 776 (1982), the court ruled that "[d]enial of intervention as of right is a final appealable order, despite the grant of permissive intervention." App. to Pet. for Cert. A-26. The court ordered further briefing on the merits of the intervention application, and ultimately held that CNA must be allowed to intervene as of right. United States v. Stringfellow, 755 F. 2d 1383 (1985) (order). See also 783 F. 2d 821 (1986) (opinion).

We granted certiorari to resolve the conflict among the Courts of Appeals as to whether this type of pretrial order is subject to immediate appeal. 476 U. S. 1157. We now vacate and remand.

II

CNA acknowledges that the District Court order in this case is not "final" in the traditional sense. The decision con

'Section 1291 provides: "The courts of appeals . . . shall have jurisdiction of appeals from all final decisions of the district courts of the United States. ..."

'See Kartell v. Blue Shield of Massachusetts, Inc., 687 F. 2d 543, 549-550 (CA1 1982); Shore v. Parklane Hosiery Co., 606 F. 2d 354, 357 (CA2 1979); see also Wheeler v. American Home Products Corp., 582 F. 2d 891, 896 (CA5 1977).

cerning CNA's intervenor status clearly is not one that "ends the litigation on the merits and leaves nothing for the court to do but execute the judgment." See Catlin v. United States, 324 U. S. 229, 233 (1945). Instead, CNA argues that the order falls within one of the narrow categories of decisions that we have deemed final for purposes of review, even though the entire dispute has not yet been resolved.

A

CNA's primary argument is that the District Court ruling is covered by the "collateral order" exception to § 1291. This doctrine recognizes that a limited class of prejudgment orders is sufficiently important and sufficiently separate from the underlying dispute that immediate appeal should be available. Cohen v. Beneficial Industrial Loan Corp., 337 U. S. 541, 546 (1949). To qualify as a collateral order, a decision must: (i) "conclusively determine the disputed question"; (ii) "resolve an important issue completely separate from the merits of the action"; and (iii) “be effectively unreviewable on appeal from a final judgment." Coopers & Lybrand v. Livesay, 437 U. S. 463, 468 (1978) (footnote omitted). See also Firestone Tire & Rubber Co. v. Risjord, 449 U. S. 368, 375 (1981).

Although a party seeking appeal must show that all three requirements are satisfied, we find it unnecessary to address each part of the test. We assume, arguendo, that the District Court order conclusively determined CNA's right to intervene, and that the intervention issue is completely separate from the merits of the underlying action. We nevertheless find that the order is not "collateral" within the meaning of Coopers & Lybrand. We conclude that because CNA is now a party to the suit by virtue of its permissive intervention, it can obtain effective review of its claims on appeal from the final judgment.

An intervenor, whether by right or by permission, normally has the right to appeal an adverse final judgment by a

trial court. See Fishgold v. Sullivan Drydock & Repair Corp., 328 U. S. 275, 280–283 (1946); Kartell v. Blue Shield of Massachusetts, Inc., 687 F. 2d 543 (CA1 1982). See also 3B J. Moore & J. Kennedy, Moore's Federal Practice ¶24-15, pp. 24-169-24-170 (2d ed. 1985) (An intervenor may appeal from "all interlocutory and final orders that affect him . . whether the right under which he intervened was originally absolute or discretionary"); 7C C. Wright, A. Miller, & M. Kane, Federal Practice and Procedure § 1923, p. 517 (2d ed. 1986). Thus if CNA still wishes to challenge the denial of intervention as of right, or if it believes that the restrictions imposed by the District Court prevented it from protecting its interests, it can raise these claims before the Court of Appeals after the trial. That court then can decide whether the order was erroneous, and if so, whether CNA's inability to participate more fully in the proceedings may have affected the final judgment. We therefore cannot conclude that CNA's interests will be "irretrievably lost in the absence of an immediate appeal." See Richardson-Merrell Inc. v. Koller, 472 U. S. 424, 431 (1985).

CNA does not dispute that it has the right to pursue a post-trial appeal. But it argues that, given the realities of complex litigation, a dispute over the right to intervene must be resolved before trial if it is to have any practical significance. CNA argues that once the district court enters a remedial order in a case such as this, involving numerous parties and years of litigation, an appellate court will be reluctant to vacate the judgment because of an erroneous intervention order. CNA suggests that the incentives to affirm the trial court's decision will be so strong at that point that the "right" to appeal will be academic at best, and thus CNA's ability to press for the strongest possible clean-up order will indeed be "irretrievably lost."

This contention may be true to some degree, but it is largely beside the point. Although it may be difficult for CNA to show that the harm from the intervention order is

sufficiently great to overturn the final judgment, this has little bearing on whether CNA has the right to an interlocutory appeal under the collateral order doctrine. The difficulties of which CNA complains are the same as those faced by any party who is subject to an adverse pretrial order. A party who has had one of several claims dismissed before trial, for example, may similarly believe that the chances of overturning the judgment on this ground are small, even if the dismissal turns out to be erroneous. Yet unless the district court specifically holds otherwise, challenges to this type of order can be raised only after judgment. See Fed. Rule Civ. Proc. 54(b). See also 10 Wright, Miller, & Kane, supra, § 2653, at 25-26, 31. CNA presents no compelling reason why the intervention order in this case should be treated differently. As a permissive intervenor, CNA will have the same rights of appeal from a final judgment as all other parties; we decline to extend the collateral order doctrine to provide more.

B

CNA also argues that because the District Court placed such onerous limitations on its right to participate in the case, the order should be construed as a complete denial of the right to intervene. CNA correctly notes that when an order prevents a putative intervenor from becoming a party in any respect, the order is subject to immediate review. Railroad Trainmen v. Baltimore & Ohio R. Co., 331 U. S. 519, 524-525 (1947). Even though CNA is now a party to the action, it maintains that the restrictions on discovery and the right to request additional relief so severely undermine its ability to influence the litigation that the order is not different in effect from one denying all participation. Indeed, CNA argues that unless it can challenge these restrictions immediately, it will be in a worse position than if the District Court had rejected its intervention application in full: CNA will be unable to participate effectively, and yet still will be bound by the final judgment because of its permissive