Stannous chloride (SnCl2) is a reducing agent largely employed in industry and in medical procedures. To evaluate its potential genotoxicity, several Escherichia coli strains were treated with SnCl2 and their survival rates determined. Results showed that the double mutant on specific genes for the repair of deoxyribonucleic acid damage was the most sensitive strain. Simultaneous near-UV illumination inhibited the lethal effect of SnCl2 in the wild type strain. Although the nature of the induced lesions are not known these results indicate the potential genotoxicity of SnCl2.