Vascular endothelial growth factor (VEGF) stimulates angiogenesis, but is also pro-inflammatory and plays an important role in the development of neurological disease, where it can have both attenuating and exacerbating effects. Several studies have indicated that VEGF-A (VEGF) may play a role in the pathogenesis of neurological inflammatory diseases. To assess the role of VEGF in patients with Behçet's disease with neurological involvement, VEGF was measured in the cerebrospinal fluid (CSF) of 32 patients compared to a group of 12 patients with noninflammatory neurological diseases (NIND) and 14 patients with multiple sclerosis (MS). We have also studied the expression of mRNA-VEGF (VEGF-A) in CSF and in peripheral blood mononuclear cells. The mean VEGF(CSF) was significantly increased in neuro-BD and MS patients compared to NIND patients. There was an association between neuro-BD-VEGF(CSF), and leukocyte count. A significant correlation was also observed between neuro-BD-VEGF(CSF) and CSF(%CD4) cells. As a measure of the integrity of the blood-brain barrier Q(albumin) was found correlated to VEGF(CSF). VEGF mRNA was significantly increased in neuro-BD patients compared to NIND patients. These results indicate that, VEGF may be associated with the increased percentages of CD4 cell subpopulation. The role of VEGF is within the inflammatory cascade in the mediation of blood-brain barrier disruption and not specific to Behçet's.