OBJECTIVES: To establish the long-term outcome for muscle-invasive transitional cell carcinoma of the bladder treated by radiotherapy with or without neoadjuvant cisplatin. METHODS: 159 patients with T2-T4a NX M0 bladder cancer were entered into a prospective randomized trial between June 1984 and June 1988. Follow-up was by 3-monthly cystoscopy in the first year, 6-monthly the next 2 years and yearly thereafter. Salvage surgery was performed at the discretion of the participating clinician. RESULTS: Minimum follow-up was 9 (median 11) years, at which time 29 patients (18%) remain alive. Median survival was 24 months with no difference between the treatment groups (chi(2) = 0.08, p = 0.77). Overall cystectomy rate was 24% (radiotherapy alone 20%, combined therapy 28%; p = 0.24). Median time to cystectomy from primary treatment was 12 months; range 56 days to 10 years. The risk of cystectomy was 11, 10 and 7% for the first, second and third years after radiotherapy respectively, and 8% in total after the third year. The proportion of patients alive in each successive year who had required a cystectomy was between 20 and 30% for 5 of the first 8 years after treatment. CONCLUSIONS: Salvage cystectomy is necessary in a quarter of patients after radiotherapy and this can be needed up to 10 years after treatment. During this time, multiple invasive procedures are likely to be performed, resulting in significant patient morbidity and cost. Patients should be fully counselled about the need for prolonged surveillance and the persisting risk of salvage surgery when deciding between primary cystectomy and radiotherapy.