A bisbenzylisoquinoline alkaloid, cepharanthine, significantly enhanced vinblastine, adriamycin and etoposide sensitivities in P-glycoprotein positive renal cancer cells. However, it did not show any enhancing effect on cisplatin sensitivity. Four patients with metastatic renal cell carcinomas were treated with intraarterial chemotherapy using vinblastine and/or adriamycin in combination with cepharanthine for their metastatic lesions (3 bone and 1 contralateral kidney metastases). A partial response was observed in 1 patient with femoral bone metastasis and a minor response in 1 patient with lumbar bone metastasis, although they were also treated with interferons. No adverse effects associated with cepharanthine were seen except in one patient complaining of redness and burning sense of the skin probably due to its vaso-dilatation effect.