To 62 vesical tumor patients, 30 ml of a HPC-PEP mixed solution was infused into the urinary bladder. The HPC-PEP solution was prepared by adding 15 ml of 2% hydroxypropylcellulosum (HPC) to 15 ml of peplomycin (PEP)/physiological saline solution in which 90 mg PEP had been dissolved. Accordingly, a total of 30 ml of the mixed solution was used. On day 7 after treatment, a clinical evaluation was made through endoscopic observation and urine cytodiagnosis. The results of the evaluation were expressed by assigning appropriate grades for the improvements made. As for the overall clinical effects, 10 patients demonstrated excellent improvement (CR) but 26 patients exhibited no improvement (NC). The overall clinical efficacy for all cases was 58%. When the evaluation was made according to severity (T1, T2, or T3), the results were as follows: of 43 T1 patients, 9 patients were judged CR, and 23 patients were PR; and of 15 T2 patients, 1 patient was CR and 3 patients were PR. However, all T3 patients were NC. The clinical efficacy for the T1 and T2 groups was 74.4% and 26.4%, respectively. A significant difference was observed between the T1 group and the T2 and T3 groups (p less than 0.05). Evaluation made according to the degree of histopathological differentiation (G1, G2 and G3) demonstrated the following results: of 23 G1 cases, 6 cases were CR, 9 cases were PR; of 32 G2 cases, 4 cases were CR and 16 cases were PR; and of 7 G3 cases, only 1 patient was found to be PR.(ABSTRACT TRUNCATED AT 250 WORDS)