Background/aims Vascular endothelial growth factor (VEGF) is a cytokine participating in inflammation with potent endothelial cell effects. It is produced by macrophages, neutrophils and vascular endothelial cells and can alter vessel permeability. Behcet's syndrome is a systemic inflammatory disorder with unknown etiology. Vascular endothelial dysfunction is one of the prominent features of the disease. We previously demonstrated the possible involvement of proinflammatory cytokines [tumor necrosis factor (TNF)-alpha, soluble interleukin-2 receptor (sIL-2R), interleukin (IL)-6 and IL-8], nitric oxide (NO) and adrenomedullin in the etiopathogenesis of Behcet's syndrome. Since VEGF expression is induced by these cytokines and VEGF itself is a potent stimulator of NO production with endothelial cell effects, this study aimed to investigate whether VEGF was affected during the course of Behcet's syndrome. We also assessed the possible involvement of VEGF in ocular Behcet's syndrome or in disease activity.