Severe cardiovascular adverse reactions including death have been associated with high-dose intravenous corticosteroid therapy. Some of the patients appeared to have acute hypersensitivity reactions to the corticosteroid, with rashes and bronchospasm; other problems included arrhythmias and myocardial infarctions. Most of the patients had underlying renal disease and/or were undergoing renal transplantation. All of the patients having the cardiovascular reactions associated with the corticosteroid received individual doses of at least 250 mg of methylprednisolone or its equivalent. The doses were usually administered over a 30-minute period or less. A cause-effect relationship between high-dose corticosteroid therapy and severe cardiovascular reactions has not been scientifically proved by a controlled trial, but caution is advised when high-dose corticosteroid therapy is administered.