The authors study the effects of local instillations of Thiotepa in 22 patients with superficial bladder tumours not involving the basement membrane. Thiotepa is used as an anti-recurrence agent following radical surgical treatment. The procedure consists of instilling 30 to 60 mg of Thiotepa which may be combined with 7,500 units of urokinase, depending on the age of the patient. The product is left in the bladder for two hours. The instillations are performed weekly for the first month and then monthly. The duration of the treatment varies between 18 months and 24 months. The objective responses to the treatment included a complete response in 36% of cases, where no recurrence was detected, and partial responses in 9% of cases, where the annual recurrence rate was reduced by more than 50% in the period following treatment. All the results were confirmed by statistical analysis. The tolerance of the treatment was very good.