Leukodystrophy with macrocephaly as the main features of infantile neurodegenerative disease are characteristics of Canavan's disease, L-2-hydroxyglutaric aciduria, type I glutaric aciduria, and Alexander's disease. Also occasionally described are occidental congenital muscular dystrophy, G(M)2-gangliosidosis, metachromatic leukodystrophy, Krabbe's disease, and mucopolysaccharidosis. Since 1995, over 60 patients with a new syndrome, vacuolating megalencephalic leukoencephalopathy, have been described. The syndrome is characterized by macrocephaly, a slowly progressive clinical course of ataxia, spastic paraparesis, and seizure disorder with relatively spared cognition. Unlike other leukodystrophies with macrocephaly (except Alexander's disease), no metabolic marker has been found. We describe a similar group of 12 patients from two different Jewish ethnic origins in whom consanguinity is prominent. These patients have neuroimaging features and magnetic resonance spectroscopy findings indicating that there is an initial increase in white-matter edema with subsequent cystic formation. Consistent with loss of tissue in these areas, brain metabolites are reduced. The familial incidence in this group of patients is suggestive of autosomal-recessive inheritance.