The XX male sex reversal syndrome represents a rare cause of male hypogonadism. Clinically, it is similar to Klinefelter syndrome in that patients present with small testes, elevated gonadotropins, and low to normal total testosterone levels. However, recent literature suggests this to be a distinct disease characterized by gynecomastia and short stature (when diagnosed in adulthood) or ambiguous genitalia and cryptorchidism (when diagnosed in infancy). We describe an adult patient with idiopathic hypogonadism who was found on chromosomal analysis to have a 46, XX karyotype and the SRY (Sex-determining Region Y) gene. The genetic basis of the XX male syndrome is described, and the literature of the wide range of cases is discussed. Because Our patient also had an autoimmune disorder (ie, Graves disease), and recent literature has shown that skewed X inactivation patterns are present in both the XX male syndrome and Graves disease, we propose this as a pathogenetic link between the 2 disorders.