Cadmium (Cd2+) is an environmental pollutant. In humans and animals it has no known biological benefit, but rather has genotoxic and carcinogenic effects. Comparative studies of cadmium-induced DNA single strand breaks in kidney and liver cells of female and male Harlan Sprague-Dawley rats were conducted, and the role of selenium in mitigating cadmium toxicity in male and female rats was also evaluated. Analysis of the results showed differences in organ and sex susceptibility to cadmium-induced DNA damage. There were more single strand breaks in DNA from liver and kidney cells of male rats than in those of the females. Concurrent administration of selenium with cadmium significantly (P<0.001) reduced DNA damage in male rats more than in female rats. However, administration of selenium alone induced DNA strand breaks in female rats at a rate which was significantly greater (P<0.001) than in male rats. These findings demonstrate differences in sex susceptibility to cadmium, and some variance in the ameliorative effects of selenium in male and female rats.