The preliminary results of a randomized ongoing study performed in order to evaluate the efficacy and the relative toxicity of a low dose (75 mg). BCG regimen in the treatment of superficial bladder cancer were considered. Ninety-eight patients (58 patients for prophylaxis of the recurrences of Ta-T1 papillary tumors; 40 patients for therapy of carcinoma in situ) received a 6-weeks course of 75 mg. BCG Pasteur vaccine. An additional course was given to non-responders. A maintenance therapy was administered in complete responders monthly for the first year and quarterly for the second. The prophylaxis group (TUR + BCG) was randomized vs TUR alone (40 patients = control group). Complete response in evaluated patients of the prophylaxis, control and therapy groups achieved 86%, 17% and 78%, respectively, after 18 months; 5%, 20% and 9% of patients, respectively, experienced tumor progression. As regards the toxicity, irritative disturbances (27%) and fever (16%) appeared significantly decreased in comparison with those reported in the literature. No major complications were experienced. In conclusion, the low dose (75 mg.) Pasteur BCG regimen used in our trial was effective as a prophylaxis against recurrent superficial papillary tumors and as a treatment of carcinoma in situ, with a significant decrease in toxicity.