In this study, different concentrations of two antiepileptic drugs, carbamazepine (CBZ) and oxcarbazepine (OXC), have been evaluated for genotoxicity in the wing spot test of Drosophila melanogaster. The wing spot test detects different kinds of somatic mutations and allows detection of mitotic recombinations. Third-instar larvae trans-heterozygous for two genetic markers mwh and flr, were treated at different concentrations of the drugs. Oxcarbazepine exposure concentrations were 1.88, 3.75, 7.50 and 15 mu g/ml. Carbamazepine exposure concentrations were 5, 10, 20 and 40 mu g/ml. In addition, the observed mutations were classified according to size and type of mutation per wing. CBZ was genotoxic in terms of total mutations per wing in the highest two doses; the same was true for CXC in the highest three doses. Survival rates of flies used in the experiments were significantly lower than that of the control group showing both drugs to have toxic effects to Drosophila melanogaster larvae. Clone formation frequency for 105 cells was lower in OXC than CBZ. However this was lower than the critical genotoxicity frequency of 2.0. (C) 2008 Elsevier Ltd. All rights reserved.