Data are presented concerning a case of female pseudohermaphroditism of unknown etiology. The child was born with labioscrotal fusion and clitoromegaly. From the age of 5 to the age of 25 there was no clinical evidence of a hormonal abnormality. At the age of 25 the patient presented with masculinization and Cushing's syndrome, and a left adrenal tumor was removed. The patient was restudied at the age of 29, when 21-hydroxylase deficiency was excluded. Other types of congenital adrenal hyperplasia are considered unlikely. The possible relationship between the ambiguous genitalia present at birth and the virilizing tumor diagnosed at the age of 25 is analyzed.