The relationship between lower urinary tract symptoms (LUTS) and erectile dysfunction (ED)is the result of their greater association in advanced age. Nevertheless, several investigations show that urinary tract symptoms have an independent relationship with sexual dysfunction and lower satisfaction. Likewise, the severity of LUTS correlates with the magnitude of sexual dysfunction in all age groups, which suggests a possible causal relationship. A series of hypothesis have been posed to explain the existence of a common physiopathology for LUTS and ED. Currently, this relationship between LUTS and ED is supported on four theories, which are not mutually excluding, (a) autonomic hyperactivity and metabolic syndrome hypothesis, (b) changes in nitric oxide/nitric oxide (NOS/NO) synthetase in the guanine monophosphatase pathway in penis and prostate, (c) the activation of Rho kinase and the endothelin pathway, and (d) the physiopathological consequences of pelvic arteriosclerosis. Given the contribution of sexual function to keep the quality of life, possible negative effects on sexual function should be taken into consideration when choosing treatment for benign prostatic hyperplasia. The combined therapeutic approach of these two entities (ED and LUTS)brings a benefit to the patient both in urinary symptoms and sexual sphere, although placebo controlled studies are required to confirm these data and to ascertain the role of combination therapy in the treatment of both conditions.