The structure of imbricatine (1), a cytotoxic metabolite of the starfish Dermasterias imbricata, has been determined by spectroscopic analysis and chemical degradation. Synthesis of model compounds 7 and 18 provided evidence for the absolute configuration and constitution of the benzyltetrahydroisoquinoline substructure of imbricatine. Key words: imbricatine, asteroid, alkaloid.