A 15-yr-old, apparently male, patient presented with a 2-yr history of gynecomastia and poor genital development. A normally formed, but small, penis with a phallic urethra was present, and testes were impalpable. The karyotype was 46,XX, and at laparotomy a uterus, Fallopian tubes, and ovaries were found, but there was no testicular tissue. The mother had had regular periods ever since menarche at 14 yr. She had complained of hirsutism since the birth of the child, and on examination 15 yr later had marked clitoromegaly. Serum androgens were elevated: testosterone, 4.5 nmol/L (normal, 0.5-3); dehydroepiandrosterone sulfate, 18 mumol/L (normal, 3-12); and androstenedione, 35 nmol/L (normal, 3-8). All failed to suppress with dexamethasone. Abdominal computed tomographic scan revealed a 9 X 6-cm mass in the position of the left adrenal gland. This was removed at laparotomy and found to be an adrenocortical tumor. Postoperatively, the androgens returned to normal. Virilization of a female fetus due to androgens secreted by a maternal adrenal tumor has only been described three times previously, and the presentation has never been delayed so long.