Antigenotoxic effects of Citrus aurentium L. (Rutaceae) fruit peel oil (CPO) in combination with mutagenic metals and alkylating agents were studied using the wing spot test of D. melonogoster. The four reference mutagens, potassium dichromate (K2Cr2O7), cobalt chloride (COCl2), ethylmethanesulfonate (EMS), and N-ethyl-N-nitrosourea (ENU) were clearly genotoxic. CPO alone at doses from 0.1 to 0.5% in Tween 80 was not mutagenic and did not enhance the mutagenic effect of the reference mutagens. However, antigenotoxic effects of CPO were clearly demonstrated in chronic cotreatments with mutagens and oil, by a significant decrease in wing spots induced by all four mutogens. The D. melanogoster wing spot test was found to be a suitable assay for detecting antigenotoxic effects in vivo. Environ. Mal. Mutagen. 50:483-488, 2009. (C) 2009 Wiley-Liss, Inc.