We conducted an observational study to evaluate prospectively the effectiveness of four modes of treatment for benign prostatic hyperplasia (BPH)-watchful waiting, alpha-blocker therapy, finasteride therapy, and surgery (transurethral prostatectomy). A total of 1459 men aged 48 to 84 years, who were diagnosed for the first time by physicians as having BPH in 1994 and who had not received treatment, participated in the study. During 1 year of follow-up, 1064 (72.9%) men remained on no treatment (watchful waiting), 156 (10.7%) were treated with finasteride, 198 (13.6%) were treated with an alpha-blocker, and 41 (2.8%) underwent prostatectomy. The American Urological Association (AUA) Symptom Index was administered to the cohort before the initiation of treatment in 1994, as well as 1 year later. Improvements in lower urinary tract symptoms, as measured by the AUA Symptom Index, were assessed using linear and logistic regression, adjusting for age and baseline. Men who underwent prostatectomy reported the biggest improvements in lower urinary tract symptoms, whether assessed by mean changes in symptom scores relative to no treatment (-5.44; 95% confidence interval [CI], -6.91 to -3.97) or by the odds of improving by 5 or more points on the AUA Symptom Index (odds ratio, 12.66; 95% CI, 5.93 to 27.0). Irrespective of the initial degree of symptom severity, prostate surgery resulted in larger improvements than those reported for either finasteride or alpha-blocker therapy. In this prospective, observational study, prostatic surgery was associated with statistically and clinically significant improvements in BPH symptoms.