We report here a case of Behçet's syndrome. The patient was suddenly affected by chest pain during the clinical course of the disease and developed abdominal pain and melena after 5 weeks. The diagnosis of acute anteroseptal myocardial infarction was made on the basis of the electrocardiography findings, and many perforated ulcers were confirmed in specimens of the resected colon. Coronary angiography showed constriction by 50% of the left anterior descending artery. There were no atherosclerotic changes. Pulse therapy was performed using sodium methylprednisolone succinate at a dose of 1,000 mg for 3 days, followed by oral administration of prednisolone at a dose of 60 mg/day, leading to improvement of all the symptoms after 3 weeks. The electrocardiogram findings at that time were normal. Prompt resolution of the symptoms provided by corticosteroid therapy supports the conclusion of previous studies that myocardial infarction in Behçet's syndrome may possibly be due to vasculitis of the coronary arteries. In Behçet's syndrome, myocardial infarction is rare but should be considered as one of the most important lesions that determine the prognosis.