Objectives. To retrospectively analyze intravesical bacillus Calmette- Guerin (BCG) treatment for Stage T1 grade 3 (T1G3) transitional cell carcinoma (TCC) of the bladder. Methods. Between 1984 and 1995, 78 patients with Stage T1 grade 3 tumor were treated by transurethral resection of all visible tumors and adjuvant BCG intravesical instillations. Median follow-up was 56 months (range 12 to 141). Results. After an initial induction course, 52 patients (67%) were tumor-free. Twenty-two patients (28%) had recurrent tumor after a median of 7 months (range 5 to 62). Progression occurred in 6 patients (7.7%) after a median of 18 months (range 5 to 56). Conclusions. Intravesical BCG appears to be an effective treatment for patients with Stage T1 grade 3 TCC. Patients whose tumors recur after an initial induction course may benefit from a second course of BCG. Intravesical BCG treatment may lower the tumor progression rate. Late recurrence, beyond 2 years, warrants long- term follow-up.