This is a controlled efficacy study with doxazosin (4 mg/day) in the long-term management of 64 ambulatory patients with benign prostatic hyperplasia (BPH). Doxazosin was given for 72 weeks and is being continued. Twenty-three controls were treated with prazosin (Minipress-4 mg/day) for 24 weeks, after which the results were similar in both the doxazosin (group 1) and prazosin (group 2) patients. Maximal and mean urethral flow increased by 44.8% and 43.5%, retention volume fell by 72.0% and 74.5%, obstructive symptoms decreased by 89.6% and 92.8% and irritation was alleviated by 81.6% and 85.0% in groups 1 and 2, respectively. Global score improved by 81.5% in group 1 and by 93.0% in group 2. Both doxazosin and prazosin produced good and similar therapeutic results. Doxazosin has the advantage of more convenient dosing (once daily) and unlike prazosin it does not produce orthostatic blood pressure falls; it is less toxic and better tolerated.