Nutrient minerals are essential yet potentially toxic, and homeostatic mechanisms are required to regulate their intracellular levels. Stannous ions (Sn²⁺) are not known to be essential in human nutrition, and its salts are used as food additives, (e.g., as a preservative and a colour-retention agent), biocidal preparations, and as reducing agent in production of Technetium-99m-labelled radio-pharmaceuticals. The comet assay (single cell gel electrophoresis) is widely used for the evaluation of DNA damage and repair in individual cells. The modified comet assay using lesion specific endonucleases has been employed to characterize specific classes of DNA damage. In order to assess the role of oxidative DNA damage in V79 cells treated with SnCl₂ at concentrations of 0.05, 0.1, 0.5 and 1 mM we used two enzymes: endonuclease III (Endo III) and formamidopyrimidine-DNA glycosylase (Fpg). Endo III converts oxidized pyrimidines into strand breaks, which can be detected by comet assay. Fpg is involved in the first step of the base excision repair to remove specific modified bases from DNA, creating an apurinic or apyrimidinic site (AP-site), which is subsequently cleaved by its AP lyase activity, giving a gap in the DNA strand. Our present results showed genotoxic effects of stannous chloride in the comet assay. Under the experimental conditions, an increase of DNA damage was induced by SnCl₂ at concentration range from 0.05 to 1 mM that is significantly different in relation to the control for the highest dose used (p < 0.05). In addition, the incubation with Endo III increased the DNA migration in the comet assay that was significantly higher at concentrations of 0.5 mM SnCl₂ (p < 0.05) and 1 mM SnCl₂ (p < 0.01). Moreover, a higher level of DNA damage recognized by Fpg was observed in V79 treated with SnCl₂ at 0.1 mM (p < 0.05), 0.5 mM (p < 0.01) and 1 mM (p < 0.01) exposure levels. Our study demonstrated that SnCl₂ induces oxidative DNA damage in V79 cells as shown in comet assay with the lesion-specific enzymes Fpg and Endo III. The results suggested a higher sensitivity and specificity of the modified comet assay, as the genotoxic effect of stannous chloride was revealed at lower concentration (two-fold for Endo III and ten-fold for Fpg) in relation to the standard alkaline comet assay.