Most studies of foreign compound metabolism have been performed in a restricted number of common laboratory animal species. The examination of animals not commonly found in the laboratory may aid in understanding the effects of environmental chemicals on wild animals and in the search for better animal models for human drug metabolism. We have performed a number of studies in "exotic" animals, such as the lion, civet, genet, hyena, elephant, various bats and reptiles, and this review compares the findings with those in common laboratory animals, to explore the possibility that drug metabolism studies may aid in the zoological classification of animals.