ABSTRACT: Erectile dysfunction (ED) can be affected by androgen levels, which exert their action through the androgen receptor (AR). Androgenic action has been demonstrated to inversely correlate with a polymorphic trinucleotide CAG repeat region in the AR gene. We conducted an epidemiologic study to determine the potential association between the CAG repeat polymorphism of the AR gene and ED complaints, gonadal steroids, and sleep parameters in a large population-based sample in São Paulo, Brazil. AR CAG repeat was genotyped in 79 men with ED complaints and in 340 controls. Sleep and hormonal profiles were measured in all men. There was no association between the AR CAG repeat polymorphism and ED complaints. Moreover, there was no significant correlation among free and total testosterone, estradiol, follicle-stimulating hormone, and luteinizing hormone levels, as well as sleep parameters with the CAG repeat length, when evaluating the population as a whole, as well as subdivided into ED and control groups independently. The results were not affected when the data were analyzed in quartiles, divided by the median of the sample, or after correction for population stratification. AR CAG repeat polymorphism is not associated with ED complaints, gonadal steroids, and sleep parameters in men from a population-based sample in Brazil.