Behçet's disease is a chronic relapsing multisystemic inflammatory disorder characterized by four major symptoms (oral aphthous ulcers, genital ulcers, skin lesions, and ocular lesions) and occasionally by five minor symptoms (arthritis, gastrointestinal ulcers, epididymitis, vascular lesions, and central nervous system symptoms). Although the etiology of Behçet's disease is still unknown, there have been recent advances in immunopathogenic studies, genome-wide association studies, animal models, diagnostic markers, and new biological agents. These advances have improved the clinical understanding of Behçet's disease and have enabled us to develop new treatment strategies for this intractable disease, which remains one of the leading causes of blindness.