Despite their efficacy in the treatment of benign prostatic hyperplasia, the popularity of inhibitors of 5 α-reductase (5ARIs) is limited by their association with adverse sexual side effects. The aim of this study was to review and meta-analyze currently available randomized clinical trials evaluating the rate of sexual side effects in men treated with 5ARIs. An extensive Medline Embase and Cochrane search was performed including the following words: 'finasteride', 'dutasteride', 'benign prostatic hyperplasia'. Only placebo-controlled randomized clinical trials evaluating the effect of 5ARI in subjects with benign prostatic hyperplasia were considered. Of 383 retrieved articles, 17 were included in this study. Randomized clinical trials enrolled 24,463 in the active and 22,270 patients in the placebo arms, respectively, with a mean follow-up of 99 weeks and mean age of 64.0 years. No difference was observed between trials using finasteride or dutasteride as the active arm considering age, trial duration, prostate volume or International Prostatic Symptoms Score at enrollment. Overall, 5ARIs determined an increased risk of hypoactive sexual desire [OR = 1.54 (1.29; 1.82); p < 0.0001] and erectile dysfunction [OR = 1.47 (1.29; 1.68); p < 0.0001]. No difference between finasteride and dutasteride regarding the risk of hypoactive sexual desire and erectile dysfunction was observed. Meta-regression analysis showed that the risk of hypoactive sexual desire and erectile dysfunction was higher in subjects with lower Qmax at enrollment and decreased as a function of trial follow-up. Conversely, no effect of age, low urinary tract symptom or prostate volume at enrollment as well as Qmax at end-point was observed. In conclusion, present data show that the use of 5ARI significantly increases the risk of erectile dysfunction and hypoactive sexual desire in subjects with benign prostatic hyperplasia. Patients should be adequately informed before 5ARIs are prescribed.