Background Behcet's disease is a chronic multisystemic disorder which is characterized by a relapsing systemic inflammatory process. One of the features of Behcet's disease is endothelial dysfunction resulting from many factors. Objective and Methods: We conducted this study to show if there is any change of plasma nitrite and nitrate levels by using the enzymatic-spectrophotometric method as an indicator for nitric oxide (NO) production, considering the disease activity in patients with Behcet's disease. The study group consisted 21 patients and 20 healthy control subjects. We measured plasma nitrite and nitrate levels, and some acute-phase reactants including erythrocyte sedimentation rate, alpha-l-antitrypsin, alpha-2-macroglobulin and the neutrophil count. Blood samples were drawn before and after treatment of the patients. Results: Nitrite, nitrate and nitrite + nitrate levels in the active period of the disease were found to be decreased compared to the inactive period and the control group. No significant differences were observed in plasma nitrite and nitrate levels between the inactive period and the control group. Conclusion: It was concluded that decreased NO production in patients with Behcet's disease may have critical biological activities relevant to pathologic events in the active period of the disease.