Background: Behçet's disease is a systemic vasculitis affecting both arteries and veins, as well as caus- ing recurrent inflammatory multiorgan disease. Vascular involvement is associated with increased mortality and morbidity. Matrix metalloproteinases are released at sites of inflammation and degrade various components of the extracellular matrix. Increased levels of metalloproteinase-9 and metal- loproteinase-2 have been previously reported in Behçet's disease., Methods: In this cross-sectional study, metalloproteinase-2 and metalloproteinase-3 serum levels were investigated in 103 patients with Behçet's disease and 69 healthy controls, using Invitrogen immunoassay human metalloproteinase-2 and metalloproteinase-3 ELISA kits., Results: Serum metalloproteinase-2 and metalloproteinase-3 levels were significantly higher in the Behçet's disease group compared to healthy controls. Besides, serum metalloproteinase-3 levels were significantly higher in subgroups of Behçet's disease with aneurysmal vascular involvement and with neurological involvement. However, metalloproteinase-2 and metalloproteinase-3 serum levels did not show a positive correlation with disease activity., Conclusion: Metalloproteinase-2 and -3 may contribute to the complex pathogenesis of Behçet's dis- ease. More importantly, the detection of very high serum levels of metalloproteinase-3 may predict the formation of an aneurysm, or possibly the presence of neurological involvement in Behçet's dis- ease and may lead the clinician to make an earlier diagnosis of these complications in young male patients with high risk.