The genetic effects of environmental pollutants include mutations in somatic cells or germinal cells that are the direct result of exposure to toxicants. Biomarkers that detect such mutagenic effects have been developed and tested in field studies on wildlife populations. However, another class of genetic effects resulting from pollution exposure exists. Specifically, changes in allele frequencies of populations will occur as a result of population bottlenecks, inbreeding, or selection at loci critical for survival in polluted environments. We describe how such genetic alterations can be studied at the population level using the techniques of molecular genetics, and we predict the development of a new field, evolutionary toxicology, that will address such issues.