Hypertension is an important risk factor for erectile dysfunction (ED). Consequently, there is a high coincidence between hypertension and ED. Oral sildenafil (Viagra) is an effective treatment for ED in patients with treated or untreated hypertension. The most common adverse events of sildenafil (headache, flushing, hypotension) result from its moderate vasodilating properties. The concomitant use of sildenafil and organic nitrates is contraindicated because it may lead to a potentiation of the decreases in blood pressure and thus cause life-threatening hypotension. In contrast, the concomitant use of sildenafil and different classes of antihypertensive agents (beta-blockers, alpha-blockers, diuretics, ACE inhibitors, calcium antagonists) may lead to additive but not to potentiating blood pressure decreases. Thus, this combination is unlikely to cause clinically significant hypotension or an increased incidence of adverse events. Sildenafil is an effective and well-tolerated treatment for ED in patients taking concomitant antihypertensive medication, including those on multidrug regimens.