We report the beneficial effects of enzyme replacement therapy with mannose-terminated human glucocerebrosidase ('Ceredase') in a patient suffering from transfusion-dependent bone marrow failure due to Gaucher's disease. Treatment with low-dose enzyme infusions, given twice weekly, rapidly reversed the haematopoietic failure and incapacitating skeletal disease. It appears likely that prior splenectomy favourably influenced the response to this therapy.