Behçet's disease (BD) is a systemic vasculitis of unknown aetiology. Its pathogenesis is related to endothelial cell dysfunction, humoral immune defects, and immune system dysregulation. The aim of this study was to investigate the possible role of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) in the pathogenesis of BD. We also investigated whether disease activity, age, or duration of BD correlates with VEGF and bFGF. We studied 33 patients and 20 healthy controls. Vascular endothelial growth factor and bFGF serum levels were measured by enzyme-linked immunosorbent assay. We measured acute phase reactants, including erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). The mean serum VEGF level was significantly higher in patients with BD (398.8+/-222.2 pg/ml) than the control group (193.0+/-122.4 pg/ml) (P=0.002). The levels were similar in both active and inactive BD (P=0.675) but did not correlate with disease duration, CRP, ESR, or age (P>0.05 for each). The bFGF was below detection limits in 18 of 33 patients with BD and ten of 20 controls, and its mean serum level was higher in BD patients (42.4+/-76.9 pg/ml) than controls (29.0+/-9.1 pg/ml), but this difference was not statistically significant (P=0.232). The bFGF levels were similar in both active and inactive BD (P=0.09) and, in patients, correlated with disease duration and CRP (r=0.58, P=0.02; r=-0.57, P=0.02, respectively) but not with ESR or age (P>0.05 for each). Vascular endothelial growth factor may be more important in the pathogenesis of BD than bFGF. Neither growth factor is an activity criterion or inflammatory marker in BD.