We have analyzed one patient with a syndrome of glycerol kinase deficiency (GKD), adrenal hypoplasia (AH), mental retardation (MR) and hypogonadotropic hypogonadism (HH). Although a cytogenetic analysis of the patient failed to reveal any detectable chromosomal abnormality, Southern blot analysis, using DNA probes from the Xp21-Xp22 region, revealed a molecular deletion localized between the DXS41 and the DXS268 loci. Our results together with those of others (van Ommen et al. 1986, 1987, Francke et al. 1987, Yates et al. 1987, Chelly et al. 1988) suggest that the GK gene is located between the DXS68 and DXS268 loci. In addition, we propose a locus for HH in Xp, distal to the genes for GK and AH.