Behçet's disease (BD) is a chronic multisystemic inflammatory disorder of unknown origin consisting of oral aphthous ulcers, ocular symptoms, skin lesions, and genital ulcerations. It has many features in common with systemic vasculitides and is more prevalent in countries along the ancient Silk route. Immune-mediated mechanisms play a major role in the pathogenesis of the disease, and inflammatory mediators are also involved. BD is not considered to be an autoimmune disorder, and the character of the disease needs to be clarified. Immunological aberrations in BD have been extensively studied by many investigators; genetic factors have been related to disease susceptibility, but their exact role in the development of disease is uncertain. Environmental factors such as infectious agents have also been implicated in the etiology of BD. However, the etiopathogenesis of the disease remains to be elucidated. Factors involved in the immunopathogenesis of BD with emphasis on the role of immunological aberrations are analyzed in this review.