Crystamidine is a new Erythrina alkaloid, which has been isolated from Erythrina crysta-galli Linn. (Japanese name: Hosoba Deiko) (Leguminosae) along with six known bases, N-nororientaline (I), erybidine (II), erythraline (III), erythrinine (IV), erysodine (VI) and erysotrine (VII). Chemical and spectral investigations of crystamidine showed that it should have the stereostructure (VIII). © 1976, The Pharmaceutical Society of Japan. All rights reserved.