Background: The aim of this study was to investigate serum paraoxonase (PON1) activity in relation to homocysteine, malondialdehyde (MDA) and lipid parameters in active and inactive Behcet's disease, (BD).,Methods: A total of 46 consecutive BD patients and 25 healthy control subjects were included in the present study.,Results: Serum PON1 activity in both active and inactive BD was significantly lower compared with healthy subjects (p < 0.05). When compared to the control group, serum MDA levels were significantly higher in both active and inactive BD (p < 0.05). Serum C-reactive protein (CRP) and homocysteine concentrations were significantly higher in active BD than those in inactive BD and control subjects (p < 0.05). In addition, there was significant negative correlation between serum PON1 and MDA levels (r= -0.697, p < 0.05) and serum PON1 activity was also negatively correlated with homocysteine levels (r= -0.428, p < 0.05) in BD patients.,Conclusions: Decreased PON1 could explain the increased lipid peroxidation and oxidative stress observed in BD. Also, according to our results, we suggest that homocysteine may contribute to decreased serum PON1 activity.