Mutations in the orphan nuclear receptor DAX1 (NR0B1) cause X-linked adrenal hypoplasia congenital (AHC), a disorder characterized by primary adrenal failure, hypogonadotropic hypogonadism. and azoospermia. We tested the hypothesis that DAX1 somatic mutations in human testis may cause azoospermia. DAX1 sequencing analysis in 15 testicular biopsy samples from men with idiopathic nonobstructive azoospermia did not reveal mutations in the coding region of the gene. We conclude that somatic abnormalities in DAX1 are absent or uncommon in these patients.