INFANTILE metachromatic leukodystrophy (MLD) is a genetically determined fatal lipidosis, in which sulfatides (cerebroside sulfates) accumulate in various organs but chiefly affect the white matter of the nervous system.1-3The activity of the enzyme arylsulfatase-A (ASA) is deficient in patients with MLD. Mehl has shown that purified ASA can degrade cerebroside sulfate in vitro,4and it is postulated that ASA deficiency results in the accumulation of cerebroside sulfate.5Various forms of therapy have been attempted in an effort to alter the natural course of the disease, but none has been effective.5-8 Replacement of ASA might degrade the accumulated cerebroside sulfate and there by be an effective treatment. This paper describes the results of both intravenous and intrathecal infusion of ASA in a patient with the late infantile form of metachromatic leukodystrophy. Report of a Case The boy was born uneventfully on Aug 20, 1963 with