The isolation of a crystalline alkaloid C30H42O4N2, termed pilocereine, from the cactus Lophocereus schottii and its occurrence in the plant tissues is described. The alkaloid has been characterized by a number of derivatives and the nature of the functional groups has been investigated. Both nitrogen atoms are tertiary, one forming part of a heterocyclic ring, while of the four oxygen atoms, two are present as methoxyl groups, one as a phenolic hydroxyl group and the fourth appears to be present in an ether linkage