Four patients with Graves' disease in whom antithyroid drugs could not be used were treated by plasmapheresis preoperatively. On admission all patients had severe hyperthyroidism. All patients were treated by beta blockers, cholestyramine and inorganic iodine before plasmapheresis. Plasmapheresis course consisted of three sessions. Removed plasma was replaced by a synthetic colloid solution and human albumin other than fresh-frozen plasma. Plasmapheresis led to decreases in serum T3 concentrations >78-40% and free T4 concentrations >69%. Near-total thyroidectomy could be performed in all patients. Although screening coagulation tests were within normal limits, patients 1 and 4 experienced more blood loss than usual during the operative procedure. Plasmapheresis could be used as an alternative therapeutic option in the preoperative management of severe hyperthyroid patients with contraindications to antithyroid drugs. However, this is an invasive procedure and patients should be followed carefully for prolonged clinic/subclinic coagulopathy due to plasma exchange.