Plasmapheresis, also known as therapeutic plasma exchange, is used in the treatment of several disorders. Temporary improvement after plasmapheresis in cases with thyrotoxicosis has been reported. A 55-year-old woman presented with agranulocytosis induced by propylthiouracil and clinical signs of heart failure. Three sessions of plasmapheresis were performed. We observed an improvement of thyroid hormone levels and clinical findings as well. Plasmapheresis can be an option when drug treatment of thyrotoxicosis fails. (C) 2004 wiley-Liss, Inc.