The purpose of this book is to provide basic information on unique anatomic and physiologic characteristics, care and maintenance,common diseases, and recommended treatments for rodents, rabbits, ferrets, and nonhuman primates. It has been prepared as a guide for practicing veterinarians, veterinary students, veterinary technicians, research scientists, and others interested in learning about smaller mammals and nonhuman primates. Knowledge is the key to a familiar dictum: primum non nocere—“first do no harm.” To undertake medical care of a species with which one is unfamiliar can be dangerous. By gaining familiarity with the more significant, unique biologic features of laboratory animals, learning the most common disease processes, and applying knowledge and skills acquired during professional training, veterinarians should be capable of providing health care to these animals with a reasonable degree of competence.