Calcium metabolism was examined in 30 adult epileptic outpatients on carbamazepine monotherapy. The patients had a normal bone mass, evaluated both on the forearm (100 +/- 13 of normal) and on the total skeleton (102 +/- 15), and normal serum concentrations of 25OHD. The serum calcium was decreased (P less than 0.001) and the serum alkaline phosphatase increased (P less than 0.001). The clinical significance of our study is that monotherapy with carbamazepine does not have the side effects on bone metabolism known as "anticonvulsant osteomalacia". Our results further question the connection between liver enzyme induction and anticonvulsant osteomalacia, since carbamazepine possesses the same potency of liver enzyme induction as phenytoin. Further studies on epileptic outpatients will be necessary in order to elucidate the connection between treatment with anticonvulsant drugs and anticonvulsant osteomalacia.