This study was done in rabbits placed on a low-cholesterol (0.5 g%) and high-cholesterol (2.0 g%) diet to induce experimental atherosclerosis. The intake of fluorine in the form of NaF in water was 3 mg F(-)/kg b.w./24 h. The activity of sorbitol dehydrogenase (SDH) was increased in plasma and decreased in the liver of rabbits on the high-cholesterol diet and in animals simultaneously exposed to NaF in water. Two months of the low-cholesterol diet produced an increase in SDH activity in plasma as a direct consequence of exposure to fluoride in the diet and presumably caused by accumulation of fluoride in the liver.