1. The botanical origin of the active alkaloid of tube curare, d-tubocurarine chloride, has been established as Chondodendron tomentosum Ruiz and Pavon, N. O. Menispermaceae. 2. Procedures are described for the isolation of crystalline d-tubocurarine chloride from the desiccated extracts of freshly gathered plant material. 3. In addition to the physiologically active quaternary base there were isolated from this curare four tertiary bases: d-isochondodendrine and d-isochondodendrine dimethyl ether, neither heretofore reported as constituents of tube curare, a third alkaloid provisionally identified as l-curine and a new base for which the name d-chondocurine is proposed. The latter was shown to be of the “bebeerine” type of bisbenzylisoquinoline alkaloid and to yield a quaternary salt of high physiological potency. © 1946, American Chemical Society. All rights reserved.