Stannous dichloride is used as a reducing agent in the preparation of technetium-99m radiopharmaceuticals. We decided to evaluate the genotoxic potential of the tin (II)-glucoheptonate complex in the kit using a tester strain of Escherichia coli AB1157. Our results show that tin (II) chloride and the tin (II)-glucoheptonate complex exert a genotoxic effect in this system. While the genotoxic effect disappeared when the glucoheptonate concentration was increased, the glucoheptonate did not protect the cultures from the damaging effects of hydrogen peroxide. The ability of glucoheptonate to protect cultures from tin (II)-induced damage can be explained on the basis of its metal chelating properties.