PURPOSE: Successful management of epileptic patients requires complete control of seizures without adverse effect. The purpose of this study is to evaluate the hematologic effect and hepatic enzyme change of antiepileptic drugs in epileptic children and compare the changes of these values according to serum drug level. METHODS: The study included 89 epileptic children with antiepileptic drugs such as phenobarbital, valproate, and carbamazepine from May 1990 to July 1999. We classified these patients into 3 groups according to the drug they had taken; group 1 : patients treated by phenobarbital, group 2 : valproate, group 3 : carbamazepine. Baseline screening tests before the start of therapy for all patients included complete blood count(CBC) and differential, platelet count, serum alanine aminotransferase(ALT), aspartate aminotransferase(AST). The tests wee repeated at follow-up visits in 2nd week, 4th week, 6th week, 12th month on the new drug. We compared their mean hematologic and liver enzyme values, which were examined before and after taken the medications, such as white blood cell counts(WBC), red blood cell(RBC), platelets, hemoglobin(Hgb), hamatocrit(Hct), mean corpuscular volume(MCA), mean corpuscular hemoglobin(MCH), mean corpuscular hemoglobin concentration(MCHC), AST, and ALT. Statistically significant change of each value was observed according to drug blood levels. RESULTS: No significant differences were found between before and after medication on AST, ALT, Hgb, MCHC in all the groups. The WBC count diminished after medication of carbamazepine, significantly. But the correlation between WBC count and serum carbamazepine level was no statistically significant. The mean platelet count diminished significantly after medication of phenobarbital and valproate, and the correlation of maximum serum valproate level with the degree of platelets count was statistically significant. Statistically significant changes were found on MCV and MCH values before and after the medication in 3rd group. But it did not depend on carbamazepine blood level. CONCLUSION: Statistically significant correlations was found between the platelet count and the plasma valproate level. Significant increase of MCV and MCH, and decrease WBC count was observed after the medication of carbamazepine.