The biochemical deficiency of aspartoacylase (ASPA; EC 3.5.1.15) was established as the basic defect in Canavan disease (CD; McKusick 271900) by Matalon et al (1988). Deficiency of ASPA and accumulation of N-acetylaspartic acid (NAA) in the leukodystrophic brain of CD is unique, and has not been observed in any other nonCanavan leukodystrophies such as Alexander and Krabbe disease, metachromatic leukodystrophy, adrenoleukodystrophy or other andiagnosed leukodystrophies (Matalon et al 1989). The spongy degeneration of brain in CD is accompanied by mental retardation, megalencephaly, hypotonia and early death. The CD is inherited as a Mendelian recessive trait and is more prevalent among Ashkenazi Jews, although patients from other ethnic groups have also been reported