Gaucher disease is an inborn recessive autosomal disease due to a partial deficiency of the lysosomal enzyme beta glucocerebrosidase. The deficient activity leads to accumulation of the lipid glucocerebroside in the liver, the spleen and bone marrow with concomitant anemia and thrombocytopenia. Patients with Gaucher disease have been classified in three types: type I is the more common, neurological manifestations occur in types II and III. Enzyme replacement therapy (ERT) with modified placental human glucocerebrosidase (ceredase) or recombinant glucocerebrosidase (cerezyme) is effective in most type I Gaucher disease and has become the current standard care administered to thousand of patients worldwide. ERT has obviated the need for bone marrow transplantation and virtually eliminated the need for splenectomy. We report here the French study including adults and children. ERT of 30 to 60 U/K every two weeks as starting dose was administrated to 108 patients with severe type I Gaucher disease. ERT fully reverse many of the manifestations of the disease. ERT regimen alleviated fatigue, and hematological and visceral signs and symptoms in nearly all severely-ill patients. Skeletal responses to treatment develop much more slowly than hematological or visceral responses. Studies in pediatrics show that the disease is more severe in children. These children should be treated early in the course of their disease to avoid irreparable damage. Hematological manifestation in type II cannot be reversed with enzyme replacement. In type III treatment can rarely reverse neurological deficit. Gaucher disease is also an excellent candidate for gene therapy.