Allium Tuncelianum is a garlic species which is locally produced in Tunceli, Turkey. Garlic contains several biologically active compounds known as organosulfur compounds which are reported to have anticarcinogenic and antimutagenic effects. Present study examined the in vitro antigenotoxic activity of ethanolic extracts of A. Tuncelianum in human lymphocyte cells by chromosome aberration test. Samples of A. Tuncelianum were extracted by ethanol using soxhlet extractor. The extract was tested on human lymphocyte cell culture in vitro chromosome aberration test. The effect of ethanol extract of A. Tuncelianum at concentrations of 0.10, 0.15, 0.20, 0.25 mu l/mL were screened for chromatid and chromosome breaks, chromosome exchange as well as chromatid union and polyploid cells against negative acetone and positive control Mitomycine C. A significant decrease in the frequency of chromosomal aberration was observed for all treatments with A. Tuncelianum ethanol extract at 24 h. In conclusion, ethanol extract of A. tuncelianum significantly reduced the chromosomal aberration rate as compared with the culture treated with MMC. The results could also indicate that A. Tuncelianum could be protective against mutagenic and carcinogenic compounds when consumed through the diet.