The redox states of albumin in serum and synovial fluid (SF) were analyzed in 35 female patients with temporomandibular joint disorders and 9 asymptomatic female healthy volunteers by high-performance liquid chromatographic (HPLC) analysis. Human serum albumin (HSA) is divided by HPLC analysis into three fractions: mercaptalbumin (HMA, reduced form) and nonmercaptalbumin (HNA-1 and HNA-2, oxidized forms). It was found that the characterized values of albumin in SF of patients with the disorders were the fraction of HMA (f (HMA), 65.8 +/- 9.1%), the fraction of HNA-1 (f (HNA-1), 31.3 +/- 8.8%), and the fraction of HNA-2 (f (HNA-2), 2.9 +/- 0.9%), respectively, and similarly the values of albumin in serum of same subjects were f (HMA), 79.4 +/- 4.0%; f (HNA-1), 18.7 +/- 3.8%; and f (HNA-2), 1.9 +/- 0.5%. The HNA fractions in SF were significantly higher than those in serum (p < 0.0001). The SF of patients and even control showed more oxidative condition compared with sera of the same subjects. Each fraction of SF showed significant difference in control (p < 0.05), and greater significance in patients (p < 0.0001). Furthermore, the HNA-2 fraction (f (HNA-2), 2.9 +/- 0.9%) in SF of the patients with temporomandibular joint disorders revealed a significantly higher value (p < 0.01) than that (f (HNA-2), 1.7 +/- 0.3%) of controls. These findings suggested that SF of the temporomandibular joint is more locally oxidized than serum; thus oxidative factors are concerned in the pathogenesis of the temporomandibular joint disorders. It was also suggested that synovial albumin may play a scavenging role against the intraarticular oxidative stress.