The bisbenzylisoquinoline alkaloid dl-tetrandrine was found to have a significant inhibitory activity against the Walker intramuscular carcinosarcoma 256 in rats over a wide dosage range. Subsequent studies revealed that the dextrorotatory enantiomer, tetrandrine (1), was equally active. Tetrandrine has undergone extensive preclinical toxicological studies and has been selected for clinical trial. The promising biological activity prompted the National Cancer Institute to procure a large collection of roots of Cyclea peltata for the isolation of kilogram quantities of tetrandrine. In view of the in vivo tumor inhibitory activity of related alkaloids as well, it was deemed of interest to examine the mother liquors of the large-scale extraction of tetrandrine as a potentially unique source of new alkaloid tumor inhibitors. We report here the isolation and structural elucidation of cycleapeltine (11), cycleadrine (5), cycleacurine (19), cycleanorine (8), and cycleahomine chloride (14), five new bisbenzyltetrahydroisoquinoline alkaloids from Cyclea peltata. In addition, three related artifacts have been isolated and their structures 16, 26, and 31 have been proposed on the basis of spectroscopic and chemical evidence.