Partial cystectomy was performed for urothelium-derived bladder carcinoma in 55 patients in the period 1958-78. Ureteral re-implantation was done in 14 cases. The operative mortality was 7.3%. The five-year and ten-year survival rates were, respectively, 47.1 and 35.4%. The series was subdivided according to grade and T-stage of the tumours. The patients with a grade I or II tumour had significantly better survival rates than those with a grade III or IV tumour. T1 tumours had a more favourable outcome than T2 or T3 tumours, though the difference was not statistically significant. The ten-year prognosis was best when the tumour measured less than 1 cm, but tumour size did not otherwise influence the result. The tumour recurred in 32 (58%) of the patients, in 25 of them within 2 years of operation. The attractions of partial cystectomy include avoidance of urinary diversion and possibility of later, more radical surgery. Prophylactic antibiotic treatment is recommended in order to reduce the operative mortality and morbidity.