This study reports a case of type VII mucopolysaccharidosis (beta-glucuronidase deficiency) presenting as lethal hydrops fetalis. Skin fibroblast cultures established postmortem revealed deficient beta-glucuronidase activity. Mucopolysaccharides were stored in various cells of the brain, heart, kidney, liver, and spleen. The stages of maturation of the bones, kidneys, and brain were discrepant, the brain being the least mature organ. A delay in central nervous system maturation may account for psychomotor retardation in some patients with this enzyme deficiency.