The International Study Group's diagnostic criteria for Behçet's disease are gaining acceptance and may be further refined before the decade is over. Previously neglected clinical features of the disease, especially arterial aneurysms and phlebitis, are increasingly reported. Each poses a dilemma in the choice of treatment, which ranges from anticoagulant to immunosuppressant regimens, old and new. T-lymphocyte abnormalities, both in subpopulation and function, suggest ongoing presentation of an unknown antigen. Research on the role of HLA-B51, a split of B5, is moving centromeric to it in pursuit of a better disease marker. The choice of immunosuppressive therapy in severe disease such as uveitis and arteritis is between alkylating agents and agents that inhibit interleukin-2 production.