Purpose: Allogeneic bone marrow transplantation (BMT) is an option for some patients with chronic myelogenous leukemia (CML). We retrospectively evaluated the effect of various risk factors observed at diagnosis and at transplantation on survival, event-free survival (EFS), and relapse after BMT. Patients and Methods: Seventy-nine patients with CML in chronic phase (CP) were treated with cyclophosphamide and total body irradiation followed by BMT. Graft-versus-host disease (GVHD) prophylaxis consisted of cyclosporine (CsA) in most instances or CsA plus the use of lymphocyte- depleted bone marrow (BM). Results: Survival at 4.5 years was 52%. Stratified by age and GVHD prophylaxis, the actuarial survival was 65% (95% confidence interval [CI], 47% to 78%) in patients aged less than 30 years receiving unmanipulated BM, 33% (95% CI, 12% to 56%) in patients ≥ 30 years old receiving unmanipulated BM, and 38% (95% CI, 14% to 63%) in patients ≥ 30 years old receiving lymphocyte-depleted BM. In univariate analysis, patient age (≥ 30 years) and the use of lymphocyte-depleted BM negatively influenced EFS. When stratified by age and GVHD prophylaxis, however, ABO incompatibility, cytomegalovirus (CMV) seropositivity, and chronic GVHD significantly reduced the probability of EFS. Factors that have been associated with early death in nontransplanted patients (ie, sex, spleen size, blast and platelet counts at presentation) were not predictive of long- term survival outcome after BMT. Conclusions: The data suggest that (1) BMT should be offered early after diagnosis to all patients with CML in CP who have compatible sibling donors regardless of prognostic factors at presentation, (2) GVHD remains the principal cause of mortality after BMT in patients receiving CsA, and (3) T-cell depletion by the physical separation method of counterflow elutriation (CE) is associated with a significant risk of relapse.