Under RCRA, EPA must impose rules for the control, management, and disposal of “hazardous waste.” The definition of solid waste (DSW) issue refers to a set of complex rules for determining whether recycled hazardous secondary materials are subject to RCRA Subtitle C. The U.S. Court of Appeals for the District of Columbia (D.C.) Circuit has issued several decisions on the DSW issue; the most recent invalidated two significant provisions of EPA’s most recent DSW rule, the “along for the ride” criterion and the verified recycler exclusion. This Article argues that the D.C. Circuit broke with DSW precedent and with the traditional deferential application of both Chevron and “arbitrary and capricious” review, and that EPA’s rule should have survived. It also discusses the potential future of the DSW issue, and examines the likely outcome of the D.C. Circuit’s “hard look” review as applied to a new DSW challenge.