The alkaloid composition of the leaves of Berberis densiflora has been studied. Berberine, β-allocryptopine, oxyacanthine, glautine, thalicmidine, isocorydine, O-methylcorypalline and the new bases densinine and densiberine have been isolated. The structures of the new alkaloids have been established by a study of spectral characteristics and chemical transformations. This is the first time that any of the known alkaloids, apart from berberine, have been isolated from a plant of this species and it is the first time that β-allocryptopine and O-methylcorypalline have been isolated from the Berberis genus.