The purpose of this study is to examine the effects of enzyme replacement therapy in patients with neuronopathic Gaucher's disease and to investigate the pathogenesis of their neurological signs and symptoms. Macrophage-targeted glucocerebrosidase will be administered by intravenous infusion under the supervision of the patient's private physician at an initial dosage of 60 to 120 IU per kg of body weight weekly or every other week. Patients will be categorized as treatment responders if they display a clinically significant increase in hemoglobin concentration and a reduction in hepatic or splenic volume. Improvement in these parameters over time will be correlated with measurements for metabolic encephalopathy and radiologic, electrophysiologic and psychometric measurements of neurological involvement.