Between January 1978 and February 1984, 120 patients with superficial bladder tumors and/or carcinoma in situ were enrolled in previously reported therapeutic trials of bacillus Calmette-Guerin. Of all treated patients 78 per cent responded to initial therapy, with a followup of 13 to 120 months (median 67 months). Of the 18 patients who failed 10 were treated with repeat, intensified courses. Nine patients who had recurrent tumors within 3 to 30 months after initiation of bacillus Calmette-Guerin therapy (median 6 months) eventually ceased having recurrence. Status free of disease in the 9 patients ranged from 25 to 90 months since the last recurrence (median 64 months). With retreatment of some of the early failures, the initial success rate of 78 per cent was increased to 89 per cent. These data support the concept that intravesical immunotherapy with bacillus Calmette-Guerin should be repeated in patients who initially appear not to respond. The data also suggest that bacillus Calmette-Guerin induces a durable beneficial response rather than simply delays eventual tumor recurrence.