We report a case of spontaneous dissection of the left main coronary artery in a 32-year-old healthy woman that was unrelated with childbirth or other known risk factors. The clinical presentation was an extensive acute anterior myocardial infarction. She was treated by thrombolysis, but did not meet reperfusion criteria. Coronary angiography revealed dissection of the left main coronary artery that extended into the anterior descending and circumflex coronary arteries. Rescue angioplasty with stenting was performed. The clinical, diagnostic, and therapeutic features of this rare entity are discussed.