Behçet's disease is a systemic vasculitis of unknown etiology. The role of allergic factors and the IgE system in the etiology and pathogenesis of Behçet's disease is not yet clearly established. The aim of the study was to investigate the possible role of the allergic factors in the pathogenesis of Behçet's disease, Serum IgE, IL-4, and soluble CD23 concentrations were studied in 24 patients with active Behçet's disease and 15 healthy person. Serum IgE levels were assayed by "micro particle enzyme immunoassay" method, serum IL-4, and sCD23 by "Sandwich Enzyme Immunoassay" method using commercial kits. Serum IgE, IL-4 and soluble CD23 levels of patients were not significantly different from normal subjects. We concluded that the role of allergic factors in the pathogenesis of Behçet's disease remains to be determined.