OBJECTIVE Descriptive analysis of an intraoperative radiotherapy protocol (IOR) in the context of conservative management of invasive bladder cancer. METHOD From November 1988 to September 1994, 24 patients with invasive bladder carcinoma (20 T2, 3 T3) were included in this protocol consisting of: transurethral resection (TUR), neoadjuvant chemotherapy (M.V.C.) in 14 patients, external irradiation (x 18 MV: 48 Gy/24 F/5 weeks) with concomitant chemotherapy (cisplatin 30 mg/day-3 days-2 cycles during irradiation)-follow-up cystoscopy then surgery with IOR (E 9 MeV: 15 Gy). RESULTS The global 3-year survival was 69%. An invasive intravesical relapse developed in 3 patients (1 salvaged by cystectomy) and a superficial relapse occurred in 1 patient. One patient developed pelvic lymph node progression and 7 developed distant metastases. The early and late toxicity was acceptable with 3 cases of ureteric necrosis or stenoses resolving after medical treatment. CONCLUSION This series shows encouraging preliminary results. IOR appears to be a technique well adapted to lesions of the fixed portion of the bladder.