Six females and six males with carbohydrate-deficient glycoprotein (CDG) syndrome type I, aged 4 months to 43 years, were examined for gonadal function and electrophoretic isoform patterns of four glycoprotein hormones: FSH, LH, TSH and erythropoietin. The female patients had a hypergonadotrophic hypogonadism from an early age without detectable ovaries in three cases. In the males, testosterone levels tended to be low with normal or slightly raised gonadotrophin values. None of the four glycoprotein hormone showed any signs of carbohydrate deficiency of the same type as in many liver-synthesized circulating glycoproteins. It is concluded that females with CDG syndrome type I have primary ovarian failure, and that the syndrome does not affect the terminal charged carbohydrate portion in gonadotrophins, TSH or erythropoietin. The characteristic carbohydrate deficiency in some circulating glycoproteins is thus not a generalized feature in this disease.