A patient with far-advanced adult type Gaucher's disease was treated with solubilized, highly purified placental glucocerebrosidase administered after entrapment in human erythrocytes or by direct intravenous injection. In some instances the enzyme-containing erythrocytes were coated with gamma globulin. No toxic side effects were observed after enzyme infusion. There were suggestive, but not conclusive, findings that enzyme infusion may have been beneficial. After therapy, there was a decrease in transfusion requirement, some improvement of liver function, possible decrease in liver size, and relief of subjective symptoms. Erythrocyte and plasma glucocerebroside levels were unchanged during therapy, but there was a possibly significant decrease in leukocyte and platelet levels of the glycolipid. No changes occurred in serum acid phosphatase or angiotensin-converting enzyme activity.