Sixty patients with superficial papillary bladder cancer, Stages Ta and T1, received chemoprophylactic treatment to prevent recurrences after the complete resection of the primary lesion. The prophylactic regimen consisted of endovesical instillations alternating doxorubicin and mitomycin C. The first six instillations were given at weekly intervals. The remaining ten were given at monthly intervals beginning 4 weeks after the resection. At the mean follow-up time of 28 +/- 10 standard deviations (SD) months, 18 patients (30%) had a recurrence. Twelve of these 18 patients (20%) had a recurrence during treatment. The overall number of recurrences was 46 for a 100 patient-months recurrence rate of 2.72. Nine patients (15%) had a regression in stage and/or grade at the first recurrence, five (8.3%) had no change, and four (6.6%) had a worsening. At the first recurrence, the treatment was continued with augmented dosages of the same drugs. However, of 12 patients undergoing such second-line treatment, only two did not have further tumors. In three patients (5%), a subsequent muscle invasive tumor appeared. This two-drug treatment does not appear to be more effective than the usual one-drug prophylaxis. However, it does lead to an hypotheses about the chemosensitivity of the superficial tumors of the bladder and its correlation with the prognosis.