Gaucher disease is characterized by the accumulation of glucocerebroside, leading to enlargement of the liver and spleen and lesions in the bones. It is caused by an inherited deficiency of the enzyme glucocerebrosidase. Many mutations exist, but four of these account for over 97% of the mutations in Ashkenazi Jews, the population group in which Gaucher disease is the most common. Although there is a strong relation between the mutations and disease manifestations, genetic counseling is made difficult by the fact that within each genotype there is considerable variability in the severity of the disease. Intravenous infusion of glucocerebrosidase is an effective treatment, but the availability of enzyme replacement therapy is limited by its high cost. Marrow transplantation is also effective in treating the disease, but is rarely performed because of the risks involved. In the future gene transfer may become the treatment of choice.