Thirty two patients--23 males and 9 females with a mean age of 52.5 years--underwent planned partial cystectomy for histologically proved muscle invasive bladder cancer. Twenty patients had transitional cell carcinoma and 12 had adenocarcinoma of the bladder. One patient had well-differentiated, 18 had moderately differentiated, and 13 had poorly differentiated tumours. The tumour size was < 2 cm in 7 patients, 2-4 cm in 19 patients, and > 4 cm in 6 patients. Patients with single primary muscle invasive tumours situated in the upper half of the bladder were considered eligible for partial cystectomy. The presence of multicentric urothelial disease, of dysplasia, or carcinoma-in-situ in bladder mucosa away from the tumour on multiple random punch biopsies was considered contraindications to partial cystectomy. All patients underwent partial cystectomy with bilateral pelvic lymphadenectomy. The tumour-free margins of resection were confirmed by intraoperative frozen section examination. The bladder was closed primarily in all patients, although three patients required re-implantation of the ureter. No patient received adjuvant radiation or chemotherapy. Five patients had pathological stage B1 (T2), 18 had B2 (T3A), and 9 had C (T3B) disease. No patient had metastatic pelvic lymph nodes. There was one postoperative death due to unrelated medical cause. Five patients had minor complications that resolved with conservative measures. All patients had adequate bladder capacity of > 250 cc at 6 months after surgery, and none had symptoms attributable to reduced bladder capacity. The overall actuarial survival was 80.1% at 5 years.(ABSTRACT TRUNCATED AT 250 WORDS)