The use of an ABO-incompatible donor for BMT after total body irradiation (TBI) has no adverse effect on engraftment, incidence of GVHD or survival when donor erythrocytes and plasma are depleted from the infused marrow. The outcome of ABO-incompatible BMT following a non-TBI-containing preparative regimen has not been as well studied. We therefore performed a retrospective review of consecutive patients undergoing allogeneic BMT for myeloid leukemia after treatment with high-dose busulfan and cyclophosphamide (BUCY) between January 1984 and January 1993. Of the 199 evaluable patients, 100 had AML or myelodysplastic syndrome, 30 of which were ABO-incompatible, and 99 had CML, 35 of which were ABO-incompatible. All patients undergoing transplant received erythrocyte and plasma-depleted marrow but 14 major ABO-incompatible patients also underwent plasma exchange before transplant. T cell-depletion and purging techniques were not employed. All records were reviewed for prognostic factors including patient age, sex, diagnosis, remission status at the time of transplant, and incidence and severity of acute and chronic GVHD. Compatible and incompatible patients with myeloid leukemia did not differ with respect to age, sex, remission status of disease at the time of transplant or incidence of GVHD.(ABSTRACT TRUNCATED AT 250 WORDS)