We evaluated the immune response after BCG treatment in superficial bladder cancer analyzing the modifications induced on lymphocytic sub-populations. In 21 patients with superficial bladder cancer we performed TURB and after 12 days began the induction cycle of 6 weeks with Pasteur BCG (75 mg/50 micromilligrams), followed by one instillation monthly for one year. Before treatment every patients underwent Mantoux intradermoreaction, blood-count and determination of peripheral blood lymphocytic subpopulations. Blood-count and lymphocytic subpopulations were repeated after 1 week, after 6 weeks, after 3 months and after 1 year. During cystoscopy after 3 months every patients underwent vesical biopsy. CD4+ and CD8+ are mainly interested among lymphocytic subpopulations at the beginning: BCG decreased CD4+ value in the patients with complete response and then it increased CD4+ and reversed the ratio between CD4+ and CD8+ on vesical mucosa.