Objective To determine the effectiveness of prostatectomy in reducing symptom severity and bother and in improving disease‐specific and general quality of life. Patients and methods A prospective, cohort study was performed in National Health Service and private hospitals in the Northern, Wessex, Mersey, and South‐West Thames Health Regions which comprised 5276 men undergoing prostatectomy recruited by 101 of the 106 (96%) surgeons (specialist and non‐specialist) performing prostatectomy during a 6‐month period. Patients were assessed using the American Urological Association (AUA) Symptom Index Score, the AUA symptom bother score, disease‐specific and generic quality‐of‐life scores, the occurrence of adverse events (urinary incontinence, erectile impotence and retrograde ejaculation) and three global (general) questions on the results of their treatment. The outcome was assessed 3 months after surgery. Results Prostatectomy was effective in reducing both symptoms (initial mean score 20.1 reduced to 7.4, P P<0.001). Not all men experienced a good reduction in symptoms; 121 (3.9%) were worse, 301 (9.6%) were the same, and 721 (23%) experienced only slight improvement. The type of operation, grade of principal operator and use of pre‐operative investigations were not associated with the extent of symptomatic improvement. Changes in symptom severity were highly correlated with changes in bothersomeness and disease‐specific quality of life but not with generic quality of life. A third of men who were continent before surgery reported some incontinence 3 months later, although only 6% found it a problem. Two‐thirds of men experienced retrograde ejaculation and 31% experienced some erectile impotence following surgery. Conclusions Prostatectomy is effective in reducing symptoms in most men. Men who experience a substantial reduction in symptoms were more likely to report a favourable outcome. The study confirmed that approximately one‐third of men reported an unfavourable result 3 months after their operation.