Fourteen patients with chronic granulocytic leukemia received bone marrow grafts from HLA identical siblings. Ten patients were in blast crisis prior to grafting, three were in an accelerated phase of their disease, and one was aplastic secondary to chemotherapy. Prior to transplant all patients were conditioned with chemotherapy including cyclophosphamide plus 1,000 rad of total body irradiation. Ten patients achieved engraftment while four died 1 to 26 days after marrow infusion without functioning grafts. Two patients reveived a second infusion of donor marrow because of delayed engraftment. Neither marrow cell dose nor presence of myelofibrosis correlated with succesful engraftment. Three out of ten engrafted patients developed graft-versus-host disease. Interstitial pneumonia occurred in seven patients. The immediate cause of death was bacterial septicemia in six patients. All evidence of leukemia disappeared in nine out of ten evaluable patients. The median survival was 43 days. One patient had a complete remission of 16 months duration.