The rationale for selective alpha 1 blockade in benign prostatic hyperplasia (BPH) is based upon the observations that the prostate adenoma contains between 20% and 40% smooth muscle and the contractile properties of prostatic smooth muscle are mediated by the alpha 1 adrenoceptor. Terazosin is a selective alpha 1 adrenoceptor antagonist that is currently under clinical investigation for the treatment of clinical BPH. The United States experience with this drug is reviewed in the present report. The outcome measures used to assess the efficacy of terazosin in BPH includes Boyarsky symptom scores and uroflowmetry. The total Boyarsky symptom score decreased 55% and the peak urinary flow increased 47% following terazosin therapy in the cumulative open-label and single-blind studies. Three hundred and thirteen subjects with clinical BPH were randomised into a phase III double-blind parallel-group 3-month placebo-controlled study of once-a-day administration of terazosin. The total Boyarsky symptom score decreased 43% and 21% in the 10 mg and placebo treatment groups, respectively. The peak urinary flow increased 37% and 12% in the 10 mg and placebo-treated groups, respectively. The adverse events associated with terazosin were relatively minor and reversible. The United States experience has unequivocally demonstrated the short-term safety and efficacy of terazosin therapy in BPH. Studies are currently under way to determine the long-term safety and efficacy associated with terazosin therapy in BPH.