The long-term efficacy of bacillus Calmette-Guerin (BCG) has not been established. We describe the tumor-free status of patients 11 years after BCG treatment. Long-term followup for the patient population (mean 74.3 ± 3.5 months, range 6 to 129) yielded a 28% (29 of 104 patients) tumor-free status for a single 6-week course of BCG. Of 66 patients who received a second 6-week course of BCG for recurrent tumors after failing the initial 6-week course 27 (41%) have remained tumor-free. Overall, 56 of 104 patients (54%) remain tumor-free after 1 or 2 courses of BCG. Analysis of recurrences with respect to 3 intervals (2 or less, 2 to 5 and more than 5 years) revealed recurrence rates of 61% (63 of 104 patients), 23% (7 of 30) and 22% (5 of 23), respectively, after 1, 6-week course of BCG. Similarly, recurrence rates for the same periods for patients receiving a second 6-week course of BCG were 42% (28 of 66), 21% (6 of 28) and 23% (5 of 22), respectively. Patients receiving either 1 or 2, 6-week BCG courses who were tumor-free at 2 years experienced essentially identical recurrence rates during the 2 to 11-year followup (36% and 33%, respectively). Overall, 23 of 66 patients (35%) who were tumor-free at 2 years had recurrent tumors during the 2 to 11-year followup. We conclude that while BCG is effective therapy for superficial bladder tumors, a continuous potential for tumor recurrence exists for responding patients necessitating life-long followup.