To establish a method for reasonable clinical use of adriamycin (ADM) and pirarubicin (THP) in the intravesical chemotherapy for superficial bladder cancer, intracellular concentrations of these drugs were examined in culture cell lines (T-24, T-24/ADM and FHS736b1) with variable durations of contamination. The intracellular concentration of THP showed a plateau at 15-30 min. contamination in T-24, and in T-24/ADM, and showed the time dependence of contamination in FHS736b1, human normal bladder mucosa cell line. The intracellular concentration of ADM showed the time dependence of contamination in T-24, T-24/ADM and FHS736b1. And these concentrations of THP were 20 times higher than those of ADM. In conclusion, it seems better that THP was retained for 5-15 min. in the bladder in the intravesical chemotherapy, from the point of view of drug efficacy and preventing side effects. And it seems good that ADM was retained for more than 30 min. in the case with drug sensitive tumors.