We compared intravesical instillations with mitomycin-C (MMC), Bacillus Calmette-Guerin (BCG) Tice, and BCG-RIVM in patients with pTa-pT1 papillary carcinoma and primary carcinoma in situ (CIS) of the bladder. Nine instillations with MMC were given or 6 weekly instillations with BCG. Early recurrences were treated with additional instillations. For toxicity and efficacy 437 patients were evaluated with a median follow-up of 32 months (range 12-56). Drug-induced and bacterial cystitis were the most frequent side-effects. The number and severity of side-effects (chi 2 test) were comparable in both BCG groups, but were significantly less in the MMC group for drug-induced cystitis (P = 0.009), other local side-effects (P = 0.004) and systemic side-effects (P < 0.001). The disease-free percentage (log-rank test) showed no significant difference for the three arms for papillary tumours (P = 0.08), nor the CIS (P = 0.20), although for CIS numbers are small. Additional instillations did not influence toxicity or efficacy.