In order to reduce the recurrence rate of bladder tumours, 78 patients with bladder tumours have been treated since November 1973 with topical Thio-TEPA bladder instillations. This method was used as an adjuvant to other forms of therapy. At the time of this review 20 of the patients have been followed up for at least one year following the onset of Thio-TEPA treatment. The total number of recurrences in these patients seems to be reduced. Advantages of topical therapy and indications for treatment are discussed.