Bone turnover has been investigated in 12 epileptic patients before and after treatment with carbamazepine and in 15 sex- and age-matched control subjects. We found higher values of markers of bone formation (serum bone alkaline phosphatase, osteocalcin, and propeptides of types I and III procollagen) and of bone resorption (serum telopeptide of type I collagen and urine N-telopeptides of type I collagen) in patients than in controls. Our study demonstrates that carbamazepine induces an increase of bone turnover.