The bark of Strychnos toxifera Schomb. has been found to contain mainly quaternary alkaloids, together with a small amount of non-quaternary bases. Fractionation of the quaternary material by adsorption and partition chromatography has yielded three new alkaloids named hemitoxiferine-I, macusine-A, and macusine-B, together with the known xanthocurine. The properties of the new alkaloids are described. The series of toxiferines isolated by King from Strychnos toxifera bark has been re-examined and several of the alkaloids have been identified.