The structure of longicaudatine, a novel bis-indole alkaloid isolated from several Strychnos species, has been elucidated chiefly by 400-MHz 1H NMR and 13C NMR spectroscopy. In some species this alkaloid co-occurs with bisnor-C-alkaloid H, an isomeric base which has similar chromatographic and chromogenic properties. © 1983, American Chemical Society. All rights reserved.