Glucocerebrosidase from human placenta has been purified to homogeneity and characterized kinetically. The carbohydrate content of the purified protein is 6%; composition and structure of the sugar moieties have been estimated. The molecular weight of the enzyme is 67,000 daltons. Several different isoelectric forms of the enzyme from white cells have been identified. Further work led to the identification of multiple allelic mutations in Gaucher's disease which distinguish the clinical sub-types. These isozymes differ in molecular weight and preliminary evidence suggests they are processed differently during synthesis. Polyclonal and monoclonal antibodies have been raised to enzyme and work is in progress to isolate the gene. Clinical studies in the disease have (1) identified an immune defect, (2) further characterized the hepatic complications and (3) described a rational approach to the neurologic symptoms by an analysis of the neuropathology and responses to a number of neurotransmitter agonists and antagonists. Serum lipoprotein abnormalities and the role of the macrophage in manifestations of the disease are being studied. Pathogenesis of the bone lesions are being defined and therapeutic strategies have been indicated.