To ascertain if androgen insensitivity causes severe oligospermia or azoospermia we studied three unrelated, phenotypically normal men with long histories of infertility. The mean plasma concentrations and production rates of testosterone were 14.3 ng per milliliter and 10.1 mg per day, respectively, values approximately twice the average found in normal men. Serum luteinizing hormone concentrations were elevated in two of the three subjects. The specific high-affinity dihydrotestosterone binding capacity of cultured genital-skin fibroblasts was 8, 0 and 10 fmol per milligram of cellular protein, values half (or less) of those from normal men and women but similar to values in subjects with partial androgen insensitivity manifested by incomplete testicular feminization or Reifenstein syndrome. The low amount of androgen receptor and the combination of high serum gonadotropins and plasma testosterone production rates suggest that the defective spermatogenesis in these infertile men was the consequence of androgen insensitivity.