Editors' Summary: Unlike other regulatory provisions of RCRA, the mixed sewage exclusion has been largely ignored by legal and technical scholars. Industry may be overlooking a potentially attractive opportunity, however, because the exclusion exempts certain industrial wastewaters from the definition of "solid waste," thereby excluding those wastes from hazardous waste regulation under RCRA. This Article examines the mixed sewage exclusion and its implications for operating facilities. After looking at the exclusion's regulatory language, the authors discuss interpretations of the regulation under existing case law. The authors then address public policy considerations supporting the exclusion and examine the exclusion's regulatory history. The Article also responds to arguments that seek to limit the exclusion's scope. The authors conclude that despite unclear regulatory interpretations by some governmental entities, the mixed sewage exclusion is a viable compliance option for certain operations.