Behçet's disease (BD) is a multisystemic chronic vasculitis characterized by its clinical polymorphism. It concerns mainly young men and generally appears between the third and the fourth decades. Cardiac involvement in Behçet's disease is rare but represents a major prognostic factor. We report the case of a young man admitted in our department for the management of an acute coronary syndrome revealing a Behçet's disease. Coronary angiography had shown a giant thrombosed aneurysm of the left coronary artery. Surgical treatment was successfully performed and the patient had a left anterior descending coronary artery bypass using the left internal mammary artery graft.