Fissistigma oldhamii (Hemsi.) Merr. (Annonaceae) is a folk medicine which has been used for hepatomegaly, anti-inflammatory effects, anti-tumor action, and rheumatism in Taiwan and southern China (1— 3). In a preliminary bioassay, the methanolic extract of stems from F. oldhamii showed significant activity in antiplatelet aggregation. In order to understand the bioactive principles of this plant, we isolated four known compounds [two aporphine alkaloids; xylopine (1), calycinine (2); one oxoaporphine alkaloid: O-methylmoschatoline (3); one morphinandienone alkaloid: N-methyl-2,3,6-trimethoxymorphinandien-7-one (4)] and one novel morphinandienone compound, N-nor-2,3,6-trimethoxymorphinandien-7-one (5). The isolation and structure elucidation of compound 5 are described in this paper.