Canavan disease (spongy degeneration of the brain) is a rare lethal neurodegenerative disorder of infancy; fewer than 100 cases have been reported. We describe a series of nine patients with enzymatic defects and clinical features consistent with Canavan disease; in two patients the disease was proved by biopsy. All patients were examined with CT and seven with MR. In every instance, both CT and MR showed white-matter disease, sometimes sparing the external and internal capsules, the corpus callosum, and the deep cerebellar white matter. Atrophic changes were found in six patients; the changes were marked in one and slight in five. There was no obvious correlation between the severity of the white-matter disease and the clinical presentation--one patient with severe white-matter disease was clinically normal. The CT and MR findings in Canavan disease are nonspecific and somewhat nonuniform: its preautopsy diagnosis relies primarily on biochemical findings.