A prospective randomized study was carried out to evaluate the efficacy of Cepharanthin (CEP) on leukocytopenia and thrombocytopenia during chemotherapy in breast cancer patients. The CEP group (51 patients) was administered CEP by 60 mg/day p.o.. The control group (55 patients) was not administered CEP in all the times. The rate of leukocytopenia was significantly lower (p less than 0.05) in the CEP group than in the control. But the recovery periods from nadir to normal range in WBC were not significantly different between the two groups. The average of nadir of WBC in the leukocytopenia patients was higher in the CEP group than in the control, but it was not significant. In MMVC group and MMC + TAM group, the rate of leukocytopenia was significantly lower in the CEP group than in the controls. The obvious efficacy of CEP for thrombocytopenia was not obtained in this study. We conclude that CEP showed an efficacy on preventing leukocytopenia induced by chemotherapy in breast cancer patients.