The anticancer effect of a podophyllotoxin derivative, etoposide (ETOP), and the vinca alkaloids, vincristine (VCR) and vindesine (VDS), on the colony forming efficiency (CFE) of B16 melanoma cells, and the CFE inhibition by the combination with a biscoclaurine alkaloid, Cepharanthine (Ceph) were studied in vitro. By combination with Ceph, CFE was reduced about 44% for ETOP, 31% for VCR and 30% for VDS compared to CFE without Ceph. Therefore, the effect of each anticancer agent was enhanced by combination with Ceph, especially that of Ceph and ETOP. The combination effect was greater when the low concentration of the agents was used. From the present study, the combination of ETOP and Ceph appears to be the more effective form of treatment.