A 23-year-old female with polymyositis received high dose intravenous immunoglobulin (IVIg) therapy. The patient suffered severe hemolytic anemia after receiving first course of IVIg infusion. This adverse reaction was likely due to allohemaglutinin A and B and from or high molecular weight IgG complexes contained in the preparation. Though this effect was observed, the treatment was repeated six times. A mild hemolysis occurred following each IVIg, with no clinical consequence. Involvement of the saturation of macrophagic receptors might explain this partial destruction of erythrocytes.