The case of a 6-year-old male patient suffering from X-chromosome-linked ichthyosis is presented. There was no steroid sulfatase activity in the proband's leucocytes and cutaneous fibroblasts. The activity was decreased in the proband's mother's leucocytes and in one brother, affected by a mild ichthyosis. Basal plasma levels of dehydroepiandrosterone and its sulfate were normal for the patient's age, suggesting that sulfates do not play a significant role in the production of free steroids. After 3 intramuscular injections of 1,500 units of human chorionic gonadotropin, plasma levels of testosterone increased normally, indicating that there was no associated primary gonadal insufficiency.