We report on the hypothalamic-pituitary-gonadal function in 2 male infants with the Smith-Lemli-Opitz (SLO or RSH) syndrome. Both infants had abnormal external genitalia. Basal and LHRH stimulated plasma gonadotropins were normal for age (1 month). Plasma testosterone, androstenedione, and dehydroepiandrosterone sulfate were normal for age and sex. Some forms of congenital adrenal hyperplasia (17,20-desmolase deficiency, 17 alpha-hydroxylase deficiency, and 3 beta-hydroxysteroid dehydrogenase deficiency) were ruled out by hormonal studies. The endocrinological findings indicate a normal hypothalamic-pituitary-gonadal function and a normal adrenal steroid biosynthesis in these 2 patients. A partial androgen receptor defect causing the genital malformations seems possible in one patient. Whether 5 alpha-reductase deficiency is the cause of the male pseudohermaphroditism in SLO syndrome remains the subject of future studies.