The present study describes the effect of fluoride (10 mg NaF/kg body weight/day) on the total protein-bound sialic acid and ceruloplasmin levels in rabbit serum after receiving sodium fluoride intragastrically for 3, 5, 8 and 10 months. The total protein-bound sialic acid and ceruloplasmin levels in serum were reduced, whereas the fluoride levels were increased showing a cumulative effect. It is suggested that the decreased circulatory sialic acid and ceruloplasmin levels with increased serum fluoride may be used in an early detection of fluorosis.