For all animal species, a good working knowledge of normal form and function is critical to the recognition of pathology. As obvious as this concept is, it is often given too little attention when we, as veterinarians, deal with reptile patients. The greatest body of credible information regarding morphology, physiology, behavior, habitat, diet and parasitology of reptiles and amphibians has been reported by biologists studying their natural history, i.e., herpetologists, comparative anatomists, physiologists, parasitologists and physiological ecologists. Therefore, the veterinarian aspiring to become a proficient reptile and amphibian practitioner should become familiar with non-veterinary source material as well as veterinary text and journals. Several perplexing cases are presented. In each instance an accurate diagnosis and effective treatment were facilitated by researching the natural history o the patient. Discussions include water metabolism strategies of the desert tortoise (Gopheus agassizii), dietary constraints of iguanid lizards (Iguana sp., Sauromalus sp.) and stress manifestations on reptiles.