High dose intravenous gammaglobulin (0.4 g/kg/day) for five days, causes a rapid rise in the platelet count in immune thrombocytopenic purpura (ITP). The response in chronic ITP is transient making it useful in emergency situations. Efficacy in immune mediated neutropenia and warm antibody haemolytic anaemia has been reported but in limited numbers. We have used this therapy in twenty-three adults with ITP, one patient with immune neutropenia, four patients with warm antibody autoimmune haemolytic anaemia and one case of thrombotic thrombocytopenic purpura (TTP). In ITP only four of the twenty patients failed to respond to gammaglobulin and of these, three had a positive antinuclear factor but no other signs of systemic lupus erythematosis. The sole patient with neutropenia treated with IgG failed to show any response. In three patients with haemolytic anaemia parameters of haemolysis improved during therapy. The patient with TTP suffered a cerebrovascular accident during therapy prior to a documented response. High dose intravenous immunoglobulin rapidly elevates the platelet count in acute and chronic ITP. Its use in other immune mediated haematological conditions has yet to be fully evaluated.