The objective of this study was to assess the efficacy and safety of sildenafil citrate (Viagra) in black American and Hispanic American men with erectile dysfunction (ED) of broad-spectrum etiology. A total of 246 black American and 197 Hispanic American men were randomized to sildenafil (50 mg, adjustable to 25 mg or 100 mg, depending on efficacy and tolerability; n = 124 and n = 99, respectively) or matching placebo (n = 122 and n = 98, respectively). After 6 weeks, patients were given the option of switching to the other blinded treatment for the following 6 weeks. The 12 weeks of double-blind treatment were followed by 12 weeks of open-label extension. Despite differences in prevalence of hypertension, diabetes mellitus, hyperlipidemia, and use of concomitant antihypertensive agents between the 2 study groups, sildenafil was efficacious and well tolerated. After 6 weeks, scores for questions 3 and 4 from the International Index of Erectile Function (IIEF) were significantly higher among sildenafil-treated black and Hispanic patients than in placebo-treated patients. In addition, compared with placebo, a significantly larger proportion of sildenafil patients reported improved erections and improved ability to have sexual intercourse. When efficacy results were stratified by ED severity or number of risk factors, scores for IIEF questions 3 and 4 were lower in men with severe ED versus mild-to-moderate ED. Similarly, the percentage of patients reporting improved erections decreased with ED severity and number of risk factors. The proportion of patients switching to the other treatment after 6 weeks was significantly higher in the placebo group (71% to 85%) than in the sildenafil group (27% to 28%). The most common adverse events included headache and vasodilation, which were mild to moderate in nature and were comparable between groups. These data demonstrate that despite differences in prevalence rates of comorbidities, efficacy and safety of sildenafil is maintained across different ethnic groups.