The isolation of a new naphthylisoquinoline alkaloid, ancistrobrevine C, from the stem bark and the roots of Ancistrocladus abbreviatus is described. Its complete structure was established by spectroscopic, chiroptical and degradative methods. For additional structural confirmation, the new alkaloid was transformed into ent-ancistrocladisine, a stereochemically well known naphthylisoquinoline. Accordingly, ancistrobrevine C is neither a real Ancistrocladaceae- nor a true Dioncophyllaceae-type alkaloid, but the first mixed, hybrid-like naphthylisoquinoline alkaloid. © 1993.