Eighteen patients with chronic granulocytic leukemia underwent allogeneic marrow transplantation from HLA-identical sibling donors. The preparative regimen included cyclophosphamide and 1000-1500 rad total body irradiation in either single or fractionated doses. Eleven patients were transplanted in blast crisis. One died too early to evaluate. Five had recurrent leukemia, three died of interstitial pneumonia (IP), and two are living in remission after 20 and 39 months. One additional patient with blast crisis was transplanted while in remission after chemotherapy and is living in remission 28 months after transplantation. Two patients were transplanted in the accelerated phase; one died early of infection and one died of IP. Four were transplanted in the chronic phase; one died of IP, one with graft-versus-host disease, and two are living in remission 11 and 25 months after transplantation.