A study on 81 patients who underwent partial cystectomy for bladder cancer is presented. The low postoperative mortality (2.46%) and the high 5-year survival (72%) show that this type of surgery is effective and without major complications. Thirty-eight patients were treated with endovesical thiotepa (OTT); the remaining 41 patients were untreated after surgery. Results showed that survival and number of relapses were similar in the two groups. This fact seems to prove that chemotherapy with OTT is not essential after segmental cystectomy. To explain this assertion, several hypotheses are presented.