We have developed a method of monitoring plasma concentrations of antiepileptic drugs which uses salivary samples, and is suitable for home monitoring in children. To validate the method, paired plasma and saliva samples from 39 children aged between 2 and 15 years were assayed for carbamazepine and its active metabolite, carbamazepine-10,11-epoxide by h.p.l.c. The method uses a gauze-wrapped cotton ball with attached string, to absorb saliva which is then separated using a syringe and plunger. There was no adsorption of CBZ and CBZ-E and they were stable over 1 month in a domestic freezer. Plasma and salivary free CBZ and CBZ-E concentrations were highly correlated (r2 = 0.99 and 0.98, respectively).