Objective: We carried out a systematic review and meta-analysis to assess the efficacy and safety of phosphodieterase-5 (PDE5) inhibitors on erectile dysfunction (ED) secondary to spinal cord injury (SCI). Methods: A literature review was performed to identify all published randomized, double-blind, placebo-controlled trials of PDE5 inhibitors for treatment of ED secondary to SCI. The search included the following database: MEDLINE, EMBASE and the Cochrane Library. The outcomes and complications analyzed involved the Global Efficacy Question (GEQ), sexual encounter profile diary question 2 and 3 (SEP2 and SEP3) and adverse events. All statistical analysis was performed using Stata 12.0 software (Stata Corp., College Station, TX, USA). Results: Six publications were used in analysis, including six randomized controlled trials that compared PDE5 inhibitors with placebo. Compared with placebo, PDE5 inhibitors were associated with significant improvements in GEQ (OR 11.997, 95% CI 8.073-17.830, Po0.0001), SEP2 (RR 1.847, 95% CI 1.561-2.185, Po0.0001) and SEP3 (RR 2.738, 95% CI 2.084-3.598, Po0.0001). Despite significant greater incidences of some adverse events observed (headache: RR 3.717, 95% CI 2.309-5.982, Po0.0001; flushing: RR 9.281, 95% CI 2.858-30.147, Po0.0001; gastrointestinal discomfort: RR 9.064, 95% CI 2.116-38.827, P = 0.003), most adverse events were mild to moderate and transient. Conclusions: This systematic review and meta-analysis indicate that PDE5 inhibitors are effective and well tolerated to treat ED secondary to SCI compared with placebo, as measured by response to GEQ, SEP2, SEP3 and incidence of adverse events. PDE5 inhibitors could be considered as the first choice in the treatment of ED patients with SCI. INTRODUCTIONApproximately 11 000 new cases are estimated to suffer from spinal cord injury (SCI) in America each year and 60% of them are between 16 and 30 years of age. Moreover, men account for 82% of all patients with SCI. 1,2 Erectile dysfunction (ED) is a common condition in individuals with SCI. 3 A high prevalence of ED is reported in about 80% of SCI patients. 4 It is an especially bothersome condition in young men who usually had an active sexual activity before their accident. 5 ED is defined as the persistent inability to achieve or maintain a penile erection for satisfactory sexual performance. 6 Most men with SCI have some type of penile erection, but it is usually not hard enough or does not last long enough for sexual life. 1 ED not only often results in disorder of self-esteem but also deteriorates partner relationship. Hence, ED has a negative effect on the life of men and their sexual partner. 7 Health-care providers deem sex life significant in the process of rehabilitation after SCI and give high priority to improving sexual activity for subjects with SCI. 8,9 Nitric oxide (NO) released by nonadrenergic-noncholinergic nerves in the penis has an important role in initiating and maintaining of the