In this study, essential oils extracted from 2 species of oregano, Origanum onites L. and Origanum minutiflorum O.Schwarz & P.H.Davis, were assayed for genotoxicity using the somatic mutation and recombination test (SMART) in Drosophila melanogaster. Results indicated that there is no significant genotoxic effect of the 2 oils tested. In addition, the antigenotoxic activities of these oils against potassium dichromate (K2Cr2O7) and cobalt chloride (CoCl2) were tested. Results indicated that essential oil cotreatments were able to abolish the genotoxic effects induced by the 2 metal compounds. It is suggested that the observed effects can be linked to the antioxidant properties of the selected essential oils. Moreover, these in vivo results will contribute to the antigenotoxicity database of the 2 Origanum species used in this study.