Several lichen species have been used for medicinal purposes throughout the ages, and they are reported to be effective in the treatment of different disorders including ulcer and cancer. It is revealed that lichens may be easily accessible sources of natural drugs and possible food supplements after their safety evaluations. The main objective in this study was to evaluate the roles of aqueous extracts of Xanthoria elegans (at 25, 50 and 100 mu g/ml) upon mitomycin C (MMC; at 10(-7) M) induced genotoxic and oxidative damages in cultured human lymphocytes. X. elegans were collected from the Erzurum and Artvin provinces (in Turkey) during August 2010. After the application of MMC and X. elegans extract (XEE), separate and together, human whole blood cultures were assessed by four genotoxicity end-points including chromosomal aberration, micronucleus, sister chromatid exchange (SCE) and 8-oxo-2-deoxyguanosine (8-OH-dG) assays. In addition, biochemical parameters [total antioxidant capacity (TAC) and total oxidative stress (TOS)] were examined to determine oxidative effects. According to our results, the frequencies of cytogenetic endpoints and 8-OH-dG levels were significantly increased by MMC compared with controls in human peripheral lymphocytes. MMC caused oxidative stress by altering TAC and TOS levels. On the contrary, XEE led to increases of TAC level without changing TOS level. XEE had no genotoxic effect. Furthermore, our findings revealed that MMC induced increases in the mean frequencies of four genotoxic indices were diminished by XEE in dose dependent manner, indicating its protective role towards cells from MMC exerted injury. In conclusion, the results obtained in the present study indicate for the first time that XEE is a potential source of natural antigenotoxicants.