Behcet's disease is a rare autoimmune vasculitis characterized by oral aphthosis, genital ulcers, and ocular and cutaneous lesions. Vascular involvement usually affects the veins more commonly than the arteries, and coronary arterial involvement is extremely rare. We report an adolescent with Behcet's disease who developed a large pseudoaneurysm of the left anterior descending coronary artery requiring a coronary arterial bypass graft.