The purpose of this study is to examine the response of the skeleton to repeated infusions of macrophage-targeted glucocerebrosidase (CEREDASE (Trademark) ) in splenectomized patients with type I Gaucher's disease. The magnitude and rate of development of the skeletal response will be monitored non-invasively. Theoretically, an enhanced response should occur in patients supplemented with pharmacologic doses of 1, 25-dihydroxyvitamin D3 (calcitriol), since calcium absorption and enzyme delivery to bone marrow macrophages should be increased in this setting. These issues will be addressed in a clinical trial that uses a modified factorial design. A total of 57 patients will be assigned to three treatment groups by block randomization.