Progression of stage T1 bladder tumors after intravesical bacillus Calmette-Guerin [published erratum appears in J Urol 1991 Apr;145(4):840] Of 221 patients with superficial bladder tumors (stages Ta, Tis and T1) treated by transurethral resection and an initial 6-week course of intravesical bacillus Calmette-Guerin (BCG) 195 were evaluated after 3 months for local response. Of these patients 17 (8.7%) had a stage T1 tumor, of whom 14 (82%) subsequently had muscle invasion (7), uncontrolled local disease (6) or metastasis (1). The median interval to progression was 8.4 months, which was significantly (p = 0.0001) less than among the other 178 patients with a nonstage T1 lesion or no tumor found at 3 months, of whom 44 (25%) had progression (median more than 5 years). These data suggest that patients with stage T1 tumor 3 months after BCG therapy require additional therapy other than simple tumor resection and meticulous followup. 