A study of 11 autopsied cases of the cerebro-hepato-renal syndrome of Zellweger (ZS) is reported. All cases had severe, persistent congenital hypotonia, hepatic lobular disarray, renal cortical cysts and pulmonary hypoplasia. Many had cardiovascular malformations, hepatomegaly, cerebral cortical gyral maldevelopment and pancreatic islet hyperplasia. Additional, less frequent findings are delineated. Results of iron content studies of hepatic and renal tissues are related to age of survival and possible development of fibrosis.