The effects of chronic fluorosis on serum biochemical parameters of cattle in the Darmous area of Morocco were studied in 50 animals. Increases in potassium, urea, gamma-globulins, lactate dehydrogenase, alkaline phosphatase and aspartate aminotransferase were observed, whereas calcium, total proteins and albumin were lowered. Such disturbances draw attention towards kidney, liver and mineral metabolism and have to be taken into account to improve the management of cattle herds in areas of chronic fluorosis.