Two recent federal appellate cases have clarified the wisdom of relying on extra-regulatory statements of the U.S. Environmental Protection Agency (EPA) not included in promulgated substantive regulations in advising clients on how to manage wastes under the Resource Conservation and Recovery Act (RCRA) regulations. Even before the May 1980 RCRA regulations appeared in the pages of the Federal Register, attorneys were debating their intended scope and applicability. After those regulations were published as final, preambles to proposed rules, reports to Congress, draft and final guidance documents, agency letters and memoranda were all referenced by the regulated community as the basis for compliance positions and enforcement defenses. Interpretations of key words and phrases within those RCRA regulations were extracted from agency statements as waste generators determined whether and how to follow or avoid various practices with respect to their waste streams. Decisions from the Tenth Circuit and District of Columbia Courts of Appeals have recently reminded all counsel working with RCRA of the limitations and risks inherent in proceeding pursuant to such informal agency interpretations.