Seventy-four consecutive patients with high-risk acute lymphoblastic leukemia (ALL) were given cyclophosphamide (CY; 50 mg/kg on each of 4 days) plus total body irradiation (TBI; 300 rad on each of 4 days) followed by a human leukocyte antigen (HLA)-identical allogeneic bone marrow transplant (BMT). Eighteen patients in first complete remission (CR1), 36 in CR2, 16 in CR3, and four in CR4 were transplanted. Patients in CR1 were transplanted 1 to 8 months (median, 3 months) after attaining CR. All 18 patients in CR1 had one or more poor risk factors: age more than 18 (N = 17), initial leukocyte count greater than or equal to 20,000 (N = 11), Ph 1 chromosome (N = 2), delay in attaining CR more than 6 weeks (N = 8), or extramedullary disease (N = 1). Of those transplanted in CR2, 72% had relapsed on therapy. The 5-year event-free survival (EFS) rates for patients transplanted in CR1, CR2, and CR3 are 42%, 43%, and 25%, respectively, at median follow-up times of 57, 54, and 72 months, respectively. Children aged less than 18 years transplanted in CR2 have a 5-year EFS rate of 54%. All CR4 patients died early after transplant. The actuarial probability of relapse is 20%, 26%, and 48% for those transplanted in CR1, CR2, and CR3, respectively. Although there was substantial transplant-associated mortality, it decreased over the decade of the study (P = .01). This study indicates that BMT offers an attractive alternative to postremission chemotherapy in patients in CR1 with poor prognostic factors and in patients in second remission.