The impact of donor-recipient ABO incompatibility on long-term BMT outcomes remains controversial. A common strategy is to deplete the donor marrow of red cells, although this variably reduces the number of CD34+ cells. This 10-year retrospective study assessed the impact of recipient plasma exchange in major ABO-incompatible allogeneic BMT on outcomes and survival. Target Ab titres were ≤ 1:4 for anti-A and ≤ 1:8 for anti-B. Patients with higher titres underwent plasma exchange before marrow infusion. Of 133 patients who underwent allogeneic BMT, 34 had a major ABO-incompatible donor. The median number of exchanges was 2 (range 1-4). There were no acute haemolytic transfusion reactions. Engraftment times, transfusion requirements and acute and chronic GVHD were no different from those of patients with an ABO-identical donor. Treatment-related mortality at 100 days was 21% in the group with a major ABO-incompatible donor and 17% in the group with an identical donor (P=0.8). Plasma exchange of the recipient is a safe method of managing donor-recipient major ABO incompatibility before BMT without the risk of haematopoietic progenitor cell loss associated with red cell depletion of the graft.