beta-Galactosylceramidase activity was deficient in leukocytes of a 5-month old child with neuro-degenerative disease. The activities of beta-galactosidase and arylsulphatase A were within normal limits. The beta-galactosylcerebrosidase activity in the mother's and father's leukocytes was 25% and 68%, respectively of the mean control values. A sharp decrease of beta-galactosylceramidase activity was found in cultured skin fibroblasts of the child. The data obtained indicate that the child suffered from globoid cell leukodystrophy (Krabbe's disease). The diagnosis was confirmed after liver and brain autopsy. The beta-galactosylceramidase was not revealed in these tissues. Typical globoid cells were observed in microscopical examination of the brain.