Hyperhaemolysis syndrome (HS), a syndrome in which there is destruction of both donor and recipient red cells after transfusion, is well recognised in patients with sickle cell disease and β-thalassaemia. It has also been reported in a patient with myelofibrosis. In acute forms of HS, evidence of red cell antibody-mediated haemolysis is lacking, and it has been proposed that the transfused and the patient's own red blood cells were destroyed by hyperactive macrophages. Continuation of transfusion may be lethal as this can further exacerbate haemolysis. We report two cases of HS successfully treated with IVIg and IV methylprednisolone. The cessation of haemolysis following administration of IVIg and IV methylprednisolone supports the view that hyperactive macrophages contribute to the RBC destruction. IVIg and methylprednisolone appear to have a synergistic effect on suppressing the activity of macrophages.