The purpose of this study was to extract the risk factors for GradeB3 leukopenia induced by docetaxel plus prednisolone (DP)therapy administered to patients with castration-resistant prostate cancer. Rates of 59% for GradeB3 leukopenia and 11% for FN were observed. On multivariate analysis, the pretreatment white blood cell count(OR=0.502, 95%CI: 0.292- 0.862, p=0.01)was significantly associated with severe leukopenia induced by DP therapy. In addition, on univariate analysis, the pretreatment platelet count, disease extent, and bilirubin level were significant factors. We consider it necessary to immediately treat patients with these risks with G-CSF.