Chromatographic separation of the EtOH extract from the aerial parts of Stephania tetrandra resulted in the isolation of a novel 4,5-dioxoaporphine alkaloid, stephadione [1], together with six known alkaloids: corydione, oxonantenine, cassameridine, nantenine, cassychicine, and tetrandrine. The structure of stephadione was determined to be 6a,7-didehydro-1,2;9,10-dimethylenedioxo-4,5-dioxo-N-methylaporphine by a consideration of spectral evidence.