During the period of therapy, leukopenia induced by chemotherapy was less severe and was cured more rapidly in the selected chronomedication group (CMG) than in the routine medication group (RMG). The incidence of leukopenia was markedly lower in CMG (12.9%) than in RMG (48.4%), and the rate of uneventful completion of chemotherapy was also higher in CMG (96.8%) than in RMG. These results suggest that selected chronomedication may be beneficial to the successful completion of chemotherapy in patients with malignant tumor.