Spinal cord injury (SCI) affects a substantial number of men who are young, active, and otherwise healthy. Erectile dysfunction (ED) is a common consequence of SCI. Since its approval, sildenafil citrate (Viagra) has been shown to effectively treat ED of various etiologies. We review the evidence for the efficacy and safety of sildenafil treatment of ED in men with SCI. A literature search identified 2 randomized controlled trials and 4 prospective case series that evaluated sildenafil treatment for ED from SCI. Efficacy was evaluated using an assessment of global efficacy and a more specific assessment of erectile function. For general efficacy, the proportion of patients who reported improved erections and ability to have intercourse was as high as 94%. Up to 72% of intercourse attempts were successful. For measures of erectile function, 5 of the 6 studies showed statistically significant improvements among sildenafil-treated versus placebo-treated patients. Erectile response rates were generally higher in patients with incomplete versus complete SCI and in patients with upper versus lower motor neuron lesions. Nevertheless, a substantial proportion of patients with complete lesions, regardless of level or lower motor neuron lesions, also benefited from sildenafil. Sildenafil was well tolerated. Incidence rates and types of adverse events that occurred in these studies were similar to those published previously. Symptoms of autonomic dysreflexia were not reported in any study. Existing evidence suggests that oral sildenafil is a highly effective and well-tolerated treatment for ED associated with SCI.