ABSTRACT: Of the many genetic diseases which are now known to be due to an enzyme deficiency, the glycolipid storage diseases are among those which are most likely to yield to enzyme replacement therapy. To be successful, such therapy requires the availability of relatively pure enzyme from a human source, delivery of the enzyme to the storage cell, and contact with the storage material for a sufficiently long period of time to permit it to be catabolized. Various receptor sites on cells may divert the delivery of enzyme to its site of action.