Sexual behavior was investigated by a sexological interview in a man with aromatase deficiency and hypogonadism. The study was performed at the end of a long testosterone treatment, during transdermal estradiol treatment and during estradiol and testosterone associated treatment. Sexual behavior did not show abnormalities. As assessed by a sexological interview and by a sexological questionnaire gender-identity was male, sexual orientation was heterosexual and libido was normal. Sexual function was limited to masturbation and was seemingly unaffected by testosterone or estradiol alone; only the associated treatment induced a great increase in libido and in frequency of masturbation and sexual fantasies when both testosterone and estradiol reached the range of normality. Sexual behavior is mainly under the control of cognitive functions in men, but sex steroids may modulate some aspects of male sexuality. Our findings suggest that in men estrogens could play a role in sexual activity.