A total of 388 men undergoing transurethral resection of the prostate for benign prostatic hypertrophy during 1988 entered a prospective cohort study designed to examine the outcome of surgery during postoperative year 1. Self-administered questionnaires were completed preoperatively, and at 3, 6 and 12 months postoperatively. The surgeons completed 1 questionnaire shortly after surgery and another questionnaire 3, 6 or 12 months later. The mortality rate during the 12 months of followup was 2.8% (11 deaths). The surgeons reported perioperative complications in 14% of the patients and immediate postoperative complications, excluding urinary tract infections, in 17%. During the first 3 months postoperatively 38% of the patients reported incontinence and 25% had a urinary tract infection. Between 6 and 12 months postoperatively only 12% of the patients were troubled by either condition. The postoperative prevalence of impotence (24%) did not alter during followup and was similar to that reported preoperatively (22%). Of the patients 74% reported feeling better and 78% experienced a decrease in the overall level of symptoms postoperatively. The improvement in symptom levels was greatest in those with the most severe preoperative symptoms, and obstructive symptoms were alleviated slightly more than irritative symptoms.