Purpose: Current treatment options for high-risk superficial TI-bladder cancer (Grade 3, associated Tis, multifocality, tumor diameter > 5 cm or multiple recurrences) include early cystectomy or the goal of organ preservation by adjuvant intravesical therapy after transurethral resection (TURB). We have evaluated the efficacy of adjuvant radiotherapy or radiochemotherapy on local control, bladder preservation, recurrence rate and long-term survival after TURB of high-risk T1-bladder cancer. Patients and Methods: From May 1982 to May 1999, a total of 74 patients with T1-bladder cancer were treated by either radiotherapy (n = 17) or concomitant radiochemotherapy (n = 57) after TURB. Radiotherapy was initiated 4 to 8 weeks after TURB; a median dose of 54 (range: 45 to 60) Gy was applied to the bladder with daily fractions of 1.8 to 2.0 Gy. Since 1985 chemotherapy has been given in the 1st and 5th week of radiotherapy and consisted of cisplatin (25 mg/m2/d) in 33 patients, carboplatin (65 mg/m2/d) was administered in 14 patients with decreased creatine clearance (< 50 ml/min). Since 1993 a combination of cisplatin (20 mg/m2/d) and 5-fluorouracil (600 mg/m2/d) was applied to 10 patients. Salvage cystectomy was recommended for patients with refractory disease or invasive recurrences. At the time of analysis, the median follow-up for surviving patients was 57 (range: 3 to 174) months. Results: After radiotherapy/radiochemotherapy, a complete remission at restaging TURB was achieved in 62 patients (83.7%), 35 of whom (47% with regard to the total cohort of the 74 treated patients) have been continuously free of tumor, 11 patients (18%) experienced a superficial relapse and 16 patients (26%) showed tumor progression after initial complete response. Overall-survival was 72% at 5 years and 50% at 10 years with 77% of the surviving patients maintaining their own bladder at 5 years. Negative prognostic factors for cancer-specific survival were non-complete (R1/2) initial TURB (p= 0.12) and recurrent disease (p = 0.07); combined radiochemotherapy was more effective than radiotherapy alone (p = 0.1). Conclusion: Adjuvant radiotherapy/radiochemotherapy offers an additional option in high-risk superficial bladder cancer with a high chance of cure and bladder preservation. The ultimate value of radiotherapy in comparison with other treatment options should be determined in randomized trials.