Previous studies have shown that Glutathione, a tripeptide found in blood, is involved in protecting against toxins. Glutathione levels are known to drop in response to cadmium. Using 15 twin pairs, we modeled the effect of cadmium on glutathione levels. The heritability of glutathione content was 91%. The application of cadmium significantly reduced the mean level of GSH. However, this reduction in GSH was not due to additive genetic influences in our sample.