Krabbe disease is an autosomal recessive inherited demyelinating disease, which is deficient in lysosomal enzyme, galactocerebrosidase. Pathophysiological characteristics of this disease are extreme demyelination in white matter and peripheral nerve, existence of globoid cells, absence of accumulation of main substrates, i.e. galactocerebrosidase in tissues and accumulation of psychosine. Molecular basis of this disease including isolation of a cDNA for human and murine galactocerebrosidase and cloning of genome of this gene are reviewed. The trial of gene therapy on twitcher, the mouse model of Krabbe disease, could break through on therapy on this progressive demyelinating disease.