We found that EPA regions have recovered $165 million of $294 million (56 percent) of the total Superfund costs from the sites we reviewed. Potentially responsible parties (PRPs) at these sites have generally paid what they have been billed. However, EPA has not recovered as much as $129 million (44 percent) and has determined it will not attempt to recover between $30 million and $90 million of this amount. This indicates a potentially significant breakdown in controls over Superfund cost recovery. Regions generally use similar billing processes to recover their Superfund costs from private parties, but exceptions exist. As a result of this evaluation, two EPA regions discovered they should have billed two sites approximately $1.8 million. These costs are now being billed. EPA regions have no formal process or information system controls to ensure staff correct costs assigned to the wrong site. Because of this lack of controls, we could not determine whether all incorrect costs were corrected and billed to the appropriate site. One EPA region did not include approximately $8 million in a negotiated settlement for a site because the costs were incorrectly assigned to another site. EPA has limited cost recovery performance measures and does not track the efficiency of cost recovery. Recommendations in this report will assist EPA in implementing improved controls for recovering Superfund costs.