The objective of this study was to correlate the severity of erectile dysfunction (ED) with the total testosterone serum levels (TT) in a normal population. During a screening program for the early diagnosis of prostate cancer, 1071 men aged from 40 to 90 y, were invited to answer the questionnaire of the Simplified International Index of Erectile Function (IIEF-5) as a method to diagnose and classify ED. The IIEF-5 scores ranged from 1 to 25 and the ED was classified into five groups according to the scores: severe (1-7), moderate (8-11), mild-moderate (12-16), mild (17-21) and no ED (22-25). Besides the questionnaire, all subjects had their TT serum levels determined based on the blood sample obtained between 08:00 and 10:00. The analysis of the relationship between the different degrees of ED and TT levels was then studied. Of the 1071 men, 965 were included in the study (90.1%). Eighty-eight percent of these were Caucasian and 12% black. The mean age of the population was 60.7 y. The prevalence of all degrees of ED was 53.9%. The degree of ED was mild in 21.5%, mild to moderate in 14.3%, moderate in 6.3% and severe in 11.9%. The variation of TT serum concentrations was similar (P>0.05) in the different age groups. Furthermore, the TT serum levels were not different for individuals with and without ED (P>0.05) and similar concentrations of TT was observed in the different severity degrees of ED (P>0.05). Only one (0.7%) man in the group of individual with maximal score had subnormal levels of TT. ED presented a clear association with the subjects' aging, but neither correlation between TT levels and ED, nor with its severity, could be demonstrated in the present study.