To evaluate the effectiveness and clinical outcome of patients treated by balloon dilatation of the prostate (BDP) compared with transurethral resection of the prostate (TURP) we performed a prospective, randomized clinical trial. Fifty-one men were randomized to either BDP or TURP. Both groups demonstrated a significant decrease in symptom score from preoperative levels (TURP 13.6 to 6.0 [p < 0.05]; BDP 14.1 to 8.1 [p < 0.01] at 1 year). The TURP group improved peak urinary flows; while, after initial improvement, the balloon group returned to pre-procedure levels. At twelve months 14 of 19 BDP patients (74%) and 14 of 18 TURP patients (78%) considered themselves improved. BDP results in symptomatic improvement; however, the effect may not persist. Objective improvement after BDP does not always occur. The morbidity of BDP is low and compares favourably to that of TURP. Thus BDP does not appear to be as effective as TURP and may offer only temporary relief of symptoms.