IN THE past 10 years there has been increased recognition of a form of pericarditis of unknown origin variously termed as idiopathic, nonspecific, viral or benign.1Attention also has been focused on the difficulties of differentiating this disease from acute myocardial infarction.2The importance of such differentiation is quite apparent from both a prognostic and a therapeutic standpoint. The following case of acute idiopathic pericarditis is reported because of a fatal outcome in a supposedly benign condition and the possible detrimental effect of the anticoagulant therapy administered. REPORT OF CASE A 52 year old white man was admitted to the Medical Service of the Veterans Administration Hospital, Dayton, Ohio, at 5:00 p.m. on July 11, 1950, with a chief complaint of pain in the chest. The patient had been in good health until 36 hours prior to admission. After ingestion of a large breakfast, there was an onset