The objective of the present study was to determine the plasma total oxidative status (TOS) and total antioxidant capacity (TAC) in patients with endemic fluorosis. A total of 7((35 males and 44 females; mean age 44.0 +/- 11.9 years) patients with endemic fluorosis and 55 (23 males and 32 females; mean age 48.3 +/- 8.5 years) age-, sex-and body mass index-matched healthy controls were included in this study. The urine fluoride levels and plasma TOS and TAC levels were measured. The urine fluoride levels of fluorosis patients were significantly higher than control subjects as expected (1.91 +/- 0.15 vs. 0.49 +/- 0.13 mg/L, respectively; p < 0.001). TOS was significantly higher in fluorosis group than in control group (17.55 +/- 3.82 vs. 15.06 +/- 4.31 mu mol H2O2 Eq/L, respectively; p = 0.001). TAC was significantly lower in fluorosis group than in control group (1.60 +/- 0.36 vs. 1.82 +/- 0.51 mmol Trolox Eq/L, respectively; p = 0.004). Oxidative stress index (OSI) was significantly higher in fluorosis group than in control group (11.5 +/- 3.8 vs. 8.8 +/- 3.7, respectively; p < 0.001). Correlation analysis in all the groups indicated that TAC was negatively correlated with urine fluoride (r = -0.25, p = 0.003), TOS was positively correlated with urine fluoride (r = 0.34, p < 0.001) and OSI was positively correlated with urine fluoride (r = 0.36, p < 0.001). The results of our study demonstrate that oxidative stress plays an important role in the pathogenesis of the endemic fluorosis.