Every year around the world veterinarians treat billions of animals, from house cats to racehorses to pythons. In this Very Short Introduction, James Yeates covers the long history of veterinary science, showing how it has developed over the past five centuries as our understanding of animals' fundamental biology, pathology, and pharmacology has grown. Considering the key roles of diagnosis, treatment, and prevention in animal health, he discusses recent challenges such as the outbreak of BSE, and antibiotic resistance. Finally, Yeates considers the future of the field, and the difficulties vets face in balancing the interests of owners and animals when they don't coincide.