655 BLACKMUN, J., concurring in judgment court obstructing the appeal." Roche, 319 U. S., at 25, citing Ex parte United States, 287 U. S. 241 (1932). Calvert, however, has neither alleged nor proved such a heedless refusal to proceed as a basis for the issuance of the writ here. Its petition offers only the bare allegation that Judge Will "in effect" abated the damages claim in deference to the state proceedings. App. 12. Judge Will has never issued such an order, and the sparse record before us will not support any such inference. So far as appears, the delay in adjudicating the damages claim is simply a product of the normal excessive load of business in the District Court, compounded by "the unfortunate consequence of making the judge a litigant" in this mandamus proceeding. Ex parte Fahey, 332 U. S. 258, 260 (1947). The judgment of the Court of Appeals is therefore Reversed. MR. JUSTICE BLACKMUN, concurring in the judgment. The plurality's opinion, ante, at 662-663, appears to me to indicate that it now regards as fully compatible the Court's decisions in Brillhart v. Excess Ins. Co., 316 U. S. 491 (1942), a diversity case, and Colorado River Water Conservation Dist. v. United States, 424 U. S. 800 (1976), a federal-issue case. I am not at all sure that this is so. I-as were MR. JUSTICE STEWART and MR. JUSTICE STEVENS was in dissent in Colorado River, and if the holding in that case is what I think it is, and if one assumes, as I do not, that Brillhart has any application here, the Court cut back on Mr. Justice Frankfurter's rather sweeping language in Brillhart, 316 U. S., at 494 495.* "Although the District Court had jurisdiction of the suit under the Federal Declaratory Judgments Act, it was under no compulsion to exercise that jurisdiction. The petitioner's motion to dismiss the bill was addressed to the discretion of the court. . . . The motion rested upon the claim that, since another proceeding was pending in a state court in which all the matters in controversy between the parties could be fully adjudicated, a declaratory judgment in the federal court was unwarranted. The correctness of this claim was certainly relevant in determining whether BRENNAN, J., dissenting 437 U.S. Because Judge Will's stay order was issued prior to this Court's decision in Colorado River, and he therefore did not have such guidance as that case affords in the area, I join in the Court's reversal of the Court of Appeals' issuance of a writ of mandamus. The issuance was premature. The Court of Appeals should have done no more than require reconsideration of the case by Judge Will in light of Colorado River. MR. CHIEF JUSTICE BURGER, dissenting. I am in general agreement with MR. JUSTICE BRENNAN'S dissenting opinion. I write separately only to emphasize that I consider it unnecessary to determine in the context of this case whether it would ever be appropriate to give res judicata effect to a state-court judgment implicating a claim over which the federal courts have been given exclusive jurisdiction. Our concern here is simply with the propriety of a federal court's delaying adjudication of such a claim in deference to a statecourt proceeding. As MR. JUSTICE BRENNAN correctly notes, whatever the proper resolution of the res judicata issue, a federal court remains under an obligation to expeditiously consider and resolve those claims which Congress explicitly reserved to the federal courts. With this minor caveat, I join MR. JUSTICE BRENNAN in his dissent. MR. JUSTICE BRENNAN, with whom THE CHIEF JUSTICE, MR. JUSTICE MARSHALL, and MR. JUSTICE POWELL join, dissenting. This case falls within none of the three general abstention categories, and the opinion of my Brother REHNQUIST there the District Court should assume jurisdiction and proceed to determine the rights of the parties. Ordinarily it would be uneconomical as well as vexatious for a federal court to proceed in a declaratory judgment suit where another suit is pending in a state court presenting the same issues, not governed by federal law, between the same parties. Gratuitous interference with the orderly and comprehensive disposition of a state court litigation should be avoided." 655 BRENNAN, J., dissenting fore strains to bring it within the principles that govern in a very narrow class of "exceptional" situations that involve "the contemporaneous exercise of concurrent jurisdictions." Colorado River Water Conservation Dist. v. United States, 424 U. S. 800, 813-818 (1976). In so straining, the opinion reaches a result supported by neither policy nor precedent, ignores difficult legal issues, misapprehends the significance of the proceedings below, and casts doubt upon a decision that has stood unquestioned for nearly 70 years. Moreover, there lurks an ominous potential for the abdication of federal-court jurisdiction in the opinion's disturbing indifference to "the virtually unflagging obligation of the federal courts to exercise the jurisdiction given them," id., at 817-for obedience to that obligation becomes all the more important when, as here, Congress has made that jurisdiction exclusive. I dissent. I Because this case came to the Court of Appeals on respondent Calvert Fire Insurance Co.'s motion for a writ of mandamus to compel Judge Will to adjudicate its claims for damages and equitable relief under the Securities Exchange Act of 1934 (1934 Act), I agree with my Brother REHNQUIST that it is essential to determine precisely what obligation the District Court had to adjudicate respondent's 1934 Act claims. That, however, is as far as my agreement goes. On the same day Calvert filed its answer to the state suit instituted against it—an answer containing a defense under the 1934 Act that the state court was required to recognize under the Supremacy Clause-it commenced an action in Federal District Court seeking relief under the 1934 Act, the Securities Act of 1933, and various state provisions. The District Court stayed all claims alleged in this complaint, other than Calvert's claim for money damages under Rule 10b-5 of the 1934 Act, pending the outcome of the state suit. Although the District Court did not formally stay the Rule 10b-5 damages claim and heard oral argument on the primary BRENNAN, J., dissenting 437 U.S. issue underlying the claim-whether a participatory interest in a reinsurance pool is a "security"-the District Court has yet to rule on this issue, so Calvert's Rule 10b-5 damages claim, like the rest of its federal suit, remains in suspension. Section 27 of the 1934 Act, 15 U. S. C. § 78aa (1976 ed.), gives the federal courts exclusive jurisdiction over claims arising under the Act. This jurisdictional grant evinces a legislative desire for the uniform determination of such claims by tribunals expert in the administration of federal laws and sensitive to the national concerns underlying them. When Congress thus mandates that only federal courts shall exercise jurisdiction to adjudicate specified claims, the "well established" principle-accepted by my Brother REHNQUIST, ante, at 662-of McClellan v. Carland, 217 U. S. 268, 282 (1910), that "the pendency of an action in the state court is no bar to proceedings concerning the same matter in the Federal court having jurisdiction," governs a multo fortiori. Yet, relying on the completely inapposite case of Brillhart v. Excess Insurance Co., 316 U. S. 491 (1942), the opinion of my Brother REHNQUIST disregards the McClellan principle and all but ignores the analysis set forth in Colorado River Water Conservation Dist. v. United States, supra, our most recent pronouncement on a district court's authority to defer to a contemporaneous state proceeding. In Brillhart, the District Court dismissed a diversity suit for a declaratory judgment because of the pendency in state court of a suit between the same parties and involving the same subject matter. The Court of Appeals reversed, holding that the dismissal was an abuse of discretion. In reversing the Court of Appeals, this Court reasoned: "Although the District Court had jurisdiction of the suit under the Federal Declaratory Judgments Act, it 1 See, e. g., Thermtron Products, Inc. v. Hermansdorfer, 423 U. S. 336, 344-345 (1976); Meredith v. Winter Haven, 320 U. S. 228, 234-235 (1943). 655 BRENNAN, J., dissenting was under no compulsion to exercise that jurisdiction. The petitioner's motion to dismiss the bill was addressed to the discretion of the court. Aetna Casualty Co. v. Quarles, 92 F.2d 321; Maryland Casualty Co. v. Consumers Finance Service, 101 F. 2d 514; American Automobile Ins. Co. v. Freundt, 103 F. 2d 613 . . . . The motion rested upon the claim that, since another proceeding was pending in a state court in which all the matters in controversy between the parties could be fully adjudicated, a declaratory judgment in the federal court was unwarranted. The correctness of this claim was certainly relevant in determining whether the District Court should assume jurisdiction and proceed to determine the rights of the parties. Ordinarily it would be uneconomical as well as vexatious for a federal court to proceed in a declaratory judgment suit where another suit is pending in a state court presenting the same issues, not governed by federal law, between the same parties." Brillhart v. Excess Insurance Co., supra, at 494 495 (emphasis added). As is readily apparent, crucial to this Court's approval of the District Court's dismissal of the suit in Brillhart were two factors absent here. First, because the federal suit was founded on diversity, state rather than federal law would govern the outcome of the federal suit. Second, and more significantly, the federal suit was for a declaratory judgment. Under the terms of the provision empowering federal courts to entertain declaratory judgment suits, 28 U. S. C. § 2201, the assumption of jurisdiction over such suits is discretionary. That section provides: "In a case of actual controversy within its jurisdiction . . . any court of the United States, upon the filing of an appropriate pleading, may declare the rights and other legal relations of any interested party seeking such declaration .. (Emphasis added.) It was primarily because federal jurisdiction over declaratory judgment suits is |