Behçet's disease (BD) is an inflammatory disease of unknown etiology. Although its pathogenesis is not fully understood, recent studies have suggested that immunological abnormalities and neutrophil hyperfunction may be involved in its etiology and pathophysiology. The immune system in BD can be characterized as a divergent cytokine production profile of the mixed Th1/Th2 cell type. In this study, we investigated the levels of interleukin (IL)-4, IL-10, IL-12, IL-13 and interferon-g in the sera of patients with BD, in comparison with recurrent aphthous stomatitis and healthy controls, to determine the Th1/Th2 profile of the disease. The levels of IL-4, IL-10 and IL-13 were found to be high in active BD patients, and IL-12 and interferon-gamma levels were lower in active BD patients than in inactive BD, recurrent aphthous stomatitis, and control patients.