Blood and urine were collected from 72 cows in six dairy herds with varying severity of dental and bone fluorotic lesions. Urinary fluoride averaged 5.13 ppm and ranged from 1.04 to 15.7 ppm fluoride. Thyroxine and triiodothyronine in serum decreased with increasing urinary fluoride, eosinophils increased, and cholesterol tended to decrease. Cattle afflicted with fluorosis developed hypothyroidism, anemia, and eosinophilia of leukocytes. Bone ash averaged 2400 ppm fluoride in 22 specimens from eight herds (range 850 to 6935 ppm fluoride). Mineral supplements were the main sources of excess fluoride. Fluoride lesions were on some cows of all herds suggesting that fluoride may affect the health and performance of some cows in "normal" herds. Fluoride lesions were on young cattle and calves in fluorosis herds.