Eighty consecutive patients were transplanted with human leukocyte antigen (HLA)-identical sibling marrow for acute myelogenous leukemia (AML, N = 29), acute lymphoid leukemia (ALL, N = 23), or chronic myelogenous leukemia (CML, N = 28). Donor marrow was depleted of lymphocytes using counterflow centrifugation. Median age of the recipients was 31 years. Pretransplant conditioning consisted of cyclophosphamide and fractionated total body irradiation (TBI) with a low (4.1 +/- 0.3 cGy/min) or high (13.1 +/- 1.6 cGy/min) midline average dose rate. In 43 patients, cytosine-arabinoside or anthracyclines were added to the conditioning regimen. Immunoprophylaxis posttransplant consisted of methotrexate (MTX) alone, cyclosporine A (CsA) in combination with MTX, or CsA alone; two patients received no immunoprophylaxis at all. Graft failure occurred in 4 of 77 evaluable patients (5%). The probability of acute graft-versus-host disease (GVHD) greater than or equal to grade 2 at day 100 after transplantation was 15%. The projected 3-year estimate of extensive chronic GVHD was 12%. Only three patients died of cytomegalovirus-interstitial pneumonitis. The projected 3-year probability of relapse was 30% (95% confidence interval [CI], range 8% to 53%) in transplants for AML in first complete remission (CR1), 35% (95% CI, 1% to 69%) after transplantation for ALL in CR1, and 38% (95% CI, 2% to 74%) after transplantation for CML in first chronic phase (CP1). The projected 3-year probability of leukemia-free survival (LFS) was 56% (95% CI, 35% to 77%) after transplantation for AML-CR1, 42% (95% CI, 16% to 69%) in patients transplanted for ALL-CR1, and 49% (95% CI, 18% to 80%) after transplantation for CML-CP1. After transplantation for AML-CR1, ALL-CR1, or CML-CP1, the median follow-up time for leukemia-free survivors was 31+, 30+, and 21+ months, respectively. Probabilities of relapse, survival, and LFS in AML-CR1 and ALL-CR1 transplants were comparable with those reported in recipients of untreated grafts. In patients transplanted for CML-CP1, probability of relapse was higher and probability of LFS was lower than in recipients of untreated grafts. In transplants for leukemia in CR1 and CP1, preparative regimen and immunoprophylaxis posttransplant were not associated significantly with the probability of acute GVHD greater than or equal to grade 2, extensive chronic GVHD, relapse, survival, or LFS. In bone marrow transplantation for leukemia, counterflow centrifugation is a useful technique for the prevention of GVHD.(ABSTRACT TRUNCATED AT 400 WORDS)