Canavan disease is a severe leukodystrophy more common among Ashkenazi Jews. The enzyme defect, apartoacylase, has been identified, and the gene cloned. Only two mutations account for over 98% of all Jewish alleles with Canavan disease. The carrier frequency among healthy Jews is 1:37-58. Carrier detection and prenatal diagnosis can be accurately carried out using molecular analysis. When mutations are unknown, analysis of amniotic fluid for NAA using stable isotope dilution technique can be used for prenatal diagnosis.