The title compound, 7,8-didehydro-4,5-epoxy-17-methylmorphinan-3,6-diyl diacetate, C21H23NO5, was crystallized from a solution of its hydrochloride and sodium acetate. Unlike prior reports in which crystals were hexagonal shaped (orthorhombic) and in space group P2(1)2(1)2(1), the crystals in the present determination grew as large prisms (monoclinic) and were in space group P2(1).