Pharmacokinetics of SM-5887, a new totally synthetic anthracycline derivative, was studied in a phase I setting by 5-day schedule. The maximum tolerated dose was 25 mg/m2/d (total dose: 125 mg/m2/body) and the dose-limiting toxicity was myelosuppression which was consistent with the results of the phase I study by a single dose. In terms of subjective side effects, decreased nausea/vomiting and increased stomatitis were observed. In pharmacokinetic study, AUC of active form of SM-5887 increased on day 5 compared to that day 1. This result suggested that 5-day schedule of SM-5887 produced an accumulation of the active form. Five-day treatment schedule of SM-5887 seems to be more tolerable and further clinical study was recommended.