Cis-diamino-dichloro-platinum (DDP) was administered to fourteen patients with a carcinoma of the bladder recurring at the original site and all analysed from a histological standpoint. All the patients had received multiple therapy previously. The tumours treated included the following: eight superficial tumours not infiltrating the chorion, four tumours involving the chorion, one tumour involving the internal muscle layer and one tumour in situ. The age range of the patients was 52 to 81 years with a mean of 69.6 years. Administration was by intra-vesical instillation of 100 mg of DDP each week for the first six weeks, then every two weeks for the next two months and finally once a month. Results were assessed on the basis of endoscopic appearance, cytology and, where applicable, biopsy. Amongst the superficial tumours not infiltrating the chorion, results were as follows: three complete remissions of respective durations of 8 months, 5 months and more than 2 months; three partial remissions of respective durations of 7 months, 6 months and 5 months; and finally two minor remissions of 5 months and 2 months. There were no failures. Amongst tumours invading the chorion, results were as follows: one complete response lasting for 10 months; 2 minor remissions of short duration: 2 months and 2 months; and one failure. Treatment of the one tumour invading the internal layer of muscle was a failure. Finally, the tumour in situ was difficult to evaluate but showed a complete response lasting for 2 months.