Editors' Summary: When citizens and local governments are confronted with problems of pollution and environmental contamination, one of their options is to use the courts to seek enforcement of environmental laws against polluters or to recover the cost of cleaning up the contamination. In this Article, or to recover the cost of cleaning up the contamination. In this Article, Mr. Babich and Mr. Hanson review the citizen suit provisions of the major federal environmental laws and CERCLA's cost recovery provisions, examine important legal issues arising under such provisions, and assess the practical effect on citizen suits of recent Supreme Court precedent in Tull v. United States and Gwaltney of Smithfield, Ltd. v. Chesapeake Bay Foundation, Inc. The authors conclude that citizen suits and cost recovery claims, though presently underutilized, can be an effective means of responding to past pollution, halting ongoing pollution, and perhaps deterring future violations.