The prevalence of benign prostatic hypertrophy (BPH) and erectile dysfunction (ED) both increase with age, and increasing evidence suggests a common cause rather than independent age-related changes. Arterial hypertension often accompanies these urological disorders, suggesting the possibility that increased alpha-adrenoceptor activity may be causal in all three conditions. As evidence for this model, alpha-adrenoceptor antagonists such as doxazosin produce therapeutically beneficial effects in lowering blood pressure, reducing prostate growth and BPH symptoms, and relieving ED. At postjunctional alpha(1)-receptors in the corpus cavernosa, noradrenaline causes vascular smooth muscle cell contraction, restricting blood flow, resulting in penile detumescence. Just as alpha-adrenoceptor antagonism results in systemic vasorelaxation to lower blood pressure, the same mechanism in the penis modulates the effects of noradrenaline to favour vasodilatation, resulting in improved erectile function. Increasing clinical evidence attests to the effectiveness of doxazosin in relieving ED, even in patients refractory to ED-specific treatment, as well as in reducing BPH symptoms and elevated blood pressure.