Behçet's disease (BD) is a systemic remitting vasculitis characterized by orogenital ulceration and uveitis. The disease is not associated with specific laboratory abnormalities. Hence, the activity of BD is generally assessed by clinical findings and--to some extent--by nonspecific markers of inflammation. This study was performed to investigate the relative efficiency of erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), serumamyloid A protein (SAA), and beta 2-microglobulin (beta 2-m) levels as markers of disease activity in patients with BD. The study population consisted of 20 patients with active BD, 23 patients with inactive BD, and 27 healthy adults serving as the control group. Serum beta 2-m, SAA, ESR, and CRP levels of patients with BD were found to be significantly higher than those in the healthy control group. They were also higher in patients with active disease than in those in remission and controls. The levels of SAA. ESR, and CRP in inactive patients were also significantly higher than the controls. No statistically significant difference was noted between beta 2-m levels of patients with inactive BD and healthy controls. Serum beta 2-m levels can beregarded as a more discriminative marker of activation in BD. The high diagnostic value of SAA levels indicate that it can also be accepted as a marker of disease activity in BD.