OBJECTIVES: To determine the outcome of men with acute urinary retention undergoing prostatectomy and to assess whether discharge with a catheter before subsequent planned re-admission for prostatectomy had an adverse effect on outcome. PATIENTS AND METHODS: A prospective cohort study was conducted of all men undergoing prostatectomy in five health care regions over a 6-month period in 56 hospitals where prostatectomies were performed under the care of 103 surgeons. The study included 3966 men undergoing prostatectomy, of whom 1242 presented with acute urinary retention; the complication rates and symptomatic outcome were assessed. RESULTS: Compared with those who underwent elective prostatectomy for symptoms alone, men presenting with acute retention had an excess risk of death at 30 days (relative risk [RR], 26.6, 95% confidence interval [CI], 3.5-204.5) and at 90 days after operation (RR 4.4, 95% CI 2.5-7.6), and an increased risk of perioperative complications. Although men with retention were older, had larger glands and had more comorbidity, these factors did not totally explain the excess risk. The final symptomatic outcome of men with acute retention was no different from that of men presenting for elective treatment. Men with retention who were managed by initial catheterization, sent home and subsequently re-admitted for planned operation had similar pretreatment characteristics, post-operative complications and outcomes to those who were kept in hospital throughout, although the men kept in hospital had a total increased length of stay. CONCLUSIONS: Men with acute retention have a high risk of developing complications after undergoing prostatectomy. We were unable to confirm that a short-term period of catheter drainage at home before re-admission for planned surgery carried increased risks of peri-operative complications.