In 17 children on carbamazepine medication alone and 15 children on combined drug regimens, carbamazepine levels were determined in paired samples of serum and mixed saliva by enzyme immunoassay. Carbamazepine levels in serum and saliva were highly correlated in within-patient and between-patient series (r=0.87–0.94). Salivary levels were altered to a minor and clinically insignificant degree by stimulation of saliva flow. Mean saliva/serum ratios, calculated from drug concentrations in saliva specimens collected without and with stimulation were 0.44–0.45 and 0.41–0.43, respectively. The saliva/serum ratio was independent of the serum carbamazepine level and was not affected by concomitant drug medication. The data indicate that measuring salivary levels by enzyme immunoassay is suitable for predicting serum carbamazepine levels. Thus, measurement of carbamazepine levels in mixed saliva samples obtained by a noninvasive technique is recommended for routine monitoring of carbamazepine medication in epileptic children.