In response to a congressional request, GAO reviewed the adequacy of the Environmental Protection Agency's (EPA) system for preventing conflicts of interest among its Superfund contractors. GAO found that: (1) prior to 1988, EPA did little before contract award to determine whether its Superfund contractors had procedures to prevent conflicts of interest; (2) although EPA periodically reviewed its contractors' performance, the reviews did not routinely verify contractor compliance with EPA conflict-of-interest requirements; (3) EPA did not properly document conflict-of-interest cases, case resolutions, or actions on contractor private-party work requests in its contract files, as required; (4) EPA did not provide contractors with specific guidance for avoiding conflicts beyond its regulations and contract clauses; and (5) EPA contracting officers differed on the information they required contractors to include in their private-party work requests, due to lack of formal guidelines and definitive criteria for evaluating contractor requests.