Sildenafil citrate, the first internationally approved and widely used oral agent for the treatment of erectile dysfunction (ED), has revolutionized the treatment of ED throughout the past 5 years. This phosphodiesterase type-5 (PDE-5) inhibitor is selective for corpus cavernosum smooth muscle tissue and produces excellent erectile function. Its efficacy and safety over a wide variety of etiologies of ED and severities of ED demonstrates its usefulness in the clinical treatment of these patients. More than 20 million men have been treated worldwide with sildenafil with excellent results. ED caused by difficult-to-treat etiologies such as radical prostatectomy, severe diabetes, and spinal cord injury have demonstrated efficacy. Although sildenafil citrate, like all PDE-5 inhibitors, is contraindicated in patients taking nitrate medications for cardiac disease, it is effective and safe for those cardiovascular patients who are not taking nitrate medications. The incidence of adverse cardiovascular events in patients taking sildenafil does not differ from those of the general population. Investigations into the pharmacologic effect of sildenafil on coronary myocardial tissue further supports the safety of this medication. Sildenafil has been safe and effective in patients taking various medications including multiple antihypertensive drugs, selective serotonin reuptake inhibitors, cardiac, and diabetic medications.