Major ABO-mismatched bone marrow transplantation (BMT) may be accompanied by red-cell haemolysis, but pure red-cell aplasia following BMT is a rare complication. Two cases of transient pure red-cell aplasia following T-lymphocyte-depleted BMT for a period of greater than 20 weeks are described, both of which responded to one cycle of plasmapheresis. The prompt response of the two patients described with red-cell aplasia with no evidence of haemolysis suggests that plasmapheresis may be considered in such clinical situations as a first treatment of choice before attempting more complex modes of therapy.