Aneurysm of the left main coronary artery is rare and is found in 0.1% of angiograms. A case of left main coronary aneurysm with no flow-limiting atherosclerotic coronary disease in a 53-year-old male is reported. In the history only a familial hypercholesterolemia was present. After some episodes of angina at rest and positive troponin, exercise myocardial scintigraphy detected a septal and inferior defect only after stress. Coronary angiography reveals an aneurysmal dilation of the left trunk involving the origin of the left anterior descending and left circumflex coronary arteries, also detected at multislice computed tomography. No intracranial or abdominal aneurysm was associated. The patient was treated medically with anticoagulant medication, low doses of beta-blockers and statins, with no adverse events at 2 and 4 months of follow-up.