Behçet's disease is a systemic inflammatory disease with a multifactorial genetic and environmental pathogenesis. The main factor of genetic predisposition is located in the HLA region. The disease is significantly linked with the HLA-B51 antigen in different ethnic groups. Recently, a linkage with MICA gene polymophism has been evidenced. This gene, located 46 kb centromerically from the HLA-B gene, codes for a non-classic HLA class I protein induced by stress and probably plays an important role in the destruction of cells targeted by Tgd lymphocytes. The functional significance of this polymorphism in Behçet's disease remains unclear.