This chapter provides examples of how environmental chemicals have impacted wildlife populations and the implications these studies have for human reproductive disorders. The groundwater in areas of heavy agricultural activity often has a distinct water quality signature composed of nitrate, potassium, calcium, magnesium, and chloride. In recent decades, amphibian populations have suffered alarming population declines and there is a growing body of evidence that environmental pesticides are contributing to this decline. The adverse effects of some pesticides, like the fungicide vinclozolin, can be transmitted through the male germ line. The notion that wildlife could have suffered adverse reproductive health effects from exposure to endocrine disruptors has led to a surge in the development of in vitro assays to screen for endocrine disruptors. The presence of intersex, gonadal characteristics of both ovary and testes in the same individual, has served as a common marker of contaminant exposure.