The aim of this investigation was the determination of the botanical source of the substance known in pharmacy as radix pareirœ bravœ, since its alkaloids are related to the phenolic alkaloids of tube- and pot-curare. This object has been attained. When pareira brava yields l-bebeerine it comes from Chondrodendron platyphyllum and when it yields d-bebeerine from Ch. microphyllum. These two species are very similar in taxonomical and pharmacognostical characters. In addition Ch. candicans from British Guiana has been examined. All these species contain bebeerine (d- or l-) and d-isochondrodendrine in widely varying proportions. A study of the properties of d-isochondrodendrine, which is now available in quantity, has enabled probable structures to be assigned to protocuridine and neoprotocuridine, isomeric phenolic alkaloids of pot-curare. From the leaves of Ch. platyphyllum a new alkaloid, chondrofoline, has been obtained. It is related to bebeerine and a probable structure is assigned. From a relatively large amount of radix pareirœ bravœ a new alkaloid, isococlaurine, isomeric with coclaurine has been isolated and its structure determined. A classification of certain bisbenzylisoquinoline alkaloids is given.