Spontaneous coronary artery dissection is a rare but morbid event. We present the case of a previously healthy 38-year-old man who experienced severe chest discomfort while vigorously exercising. An acute anterolateral myocardial infarction was diagnosed. The patient underwent coronary angiography, demonstrating acute thrombosis of the left main coronary artery. The patient was referred for immediate bypass surgery. Examination of the left main coronary artery in the operating room revealed a dissection flap with thrombosis. With successful surgical intervention, the patient made an uneventful recovery. This case is discussed and the literature reviewed.