Editors' Summary: In this Dialogue, counsel for Alcan Aluminum Corporation argues that the U.S. Supreme Court's decision in Eastern Enterprises v. Apfel has dramatic implications for CERCLA, particularly with regard to the imposition of liability for actions that occurred well before the statute was enacted. The Dialogue asserts that the retroactive impact of CERCLA upon "third-party generators"—those that arranged for the disposal of their wastes at regulated facilities—is inconsistent with both the plurality and dissenting opinions in Eastern Enterprises. It begins with an analysis of the distinction between "single-party" and "third-party" CERCLA sites. The Dialogue then examines the facts in a currently pending matter involving Alcan, and describes the rationales mentioned in earlier decisions that sustained CERCLA's retroactive application. After discussing the opinions in Eastern Enterprises, the author further contends that single-party generators satisfy the Court's criteria and should be insulated from retroactive CERCLA liability. Finally, the Dialogue surveys recent post-Eastern Enterprises decisions regarding CERCLA and describes why their holdings are incorrect.