Lower urinary tract symptoms (LUTS) and erectile dysfunction (ED) are age-related conditions that may have a profound impact on the quality of life. The relationship between LUTS and ED is not completely understood. In this study, we assessed this relationship in men over 45 years of age during a prostate cancer screening program. LUTS and ED were evaluated in 1267 men aged 45-75 years (mean 58.2+/-8.2 years). Patients completed the International Prostate Symptom Score (IPSS) and the International Index of Erectile Function-5 (IIEF-5). The association between LUTS and ED was analyzed and the influence of age in the results was tested. We also evaluated the influence of the intensity of LUTS in the ED severity. A total of 514 (40.6%) patients were considered symptomatic of LUTS (24.8% with mild, 11.8% with moderate and 4% with severe LUTS). ED was present in 758 (59.9%) men and was considered mild in 25.0%, moderate in 18.3% and severe in 16.7%. The IIEF-5 score had a negative correlation with both the IPSS score (r=-0.33, P<0.001) and age (r=-0.31 and P<0.001). Age was positively associated with the IPSS score (r=0.14 and P<0.001). A significant correlation was observed between LUTS and ED, with 57.6% of the men with LUTS presenting ED as opposed to 29.7% of the asymptomatic population (odds ratio=3.32; 95% CI =2.57-4.29, P<0.001). Age-adjusted univariate analysis revealed a significant and independent influence of LUTS on the incidence of ED (odds ratio=2.72; 95% CI=2.08-3.57, P<0.001). IIEF scores varied significantly according to the severity of the urinary symptoms. Our findings in a prostate cancer screening population confirm that LUTS is an age-independent predictor of ED. Furthermore, they demonstrate that not only the presence of LUTS increases the likelihood of developing ED, but the severity of LUTS is associated with the intensity of ED.