This study was conducted to determine the levels of nitrite and nitrate and the activities of catalase and carbonic anhydrase in the blood of sheep with and without endemic fluorosis. Blood samples from 20 fluorotic and 10 healthy Morkaraman sheep 3-4 years old in the Van area of Turkey were collected and analyzed. In the fluorotic sheep the average catalase activity level in the blood was significantly lower at 1.72 vs. 11.23 mg/Hb in the healthy sheep. On the other hand, carbonic anhydrase enzyme activities were significantly higher in the fluorotic sheep at 2.13 vs. 0.13 mg/Hb in the healthy sheep. Nitrite and nitrate levels from oxidation of nitric oxide were 2.31 and 3.32 vs. 0.51 and 0.84 ppm in the fluorotic and healthy sheep, respectively. These results have important health implications for the widespread occurrence of fluorosis among people and animals living in these areas of Turkey.