Crystalline d-tubocurarine has been isolated in good yield from curare prepared from a single plant species, namely, Chondodendron tomentosum. This result establishes with certainty the botanical origin of this compound and substantiates the supposition that it is this species which furnishes the active constituent in certain types of curare. The extract from this plant furthermore yielded two new tertiary alkaloids which could be converted into physiologically active quaternary bases. Methylation of the phenolic hydroxyl groups in the quaternary bases resulted in a 3-9-fold increase in physiological potency.