Carbamazepine (CBZ) levels in the scalp hair of seventeen patients (ten male and seven female), aged from five to forty years old, receiving the drug systematically were determined after hair dissolution and solid-phase extraction procedures using both immunoassay (Abbott TDx) and gas chromatographic (GC) techniques. Carbamazepine levels in hair ranged from 13.9 to 66.3 micrograms/g (mean 26.6 micrograms/g, median 20.9 micrograms/g) according to GC measurements. The immunoassay technique gave slightly higher results (mean 28.0 micrograms/g, median 22.1 micrograms/g). The blood concentrations of carbamazepine, using immunoassay (Abbott TDx) technique, ranged from 2.9 to 10.7 micrograms/ml (mean 6.2 micrograms/ml, median 5.7 micrograms/ml). Our data indicate the possible use of hair testing as a marker of the dosage history of patients under long-term treatment with CBZ.