The practice of veterinary medicine has changed radically over the past two decades, new technology and scientific breakthroughs have occurred, in close association with the field of human medicine. This progress has not only increased the capacity of veterinarians to provide high-quality care, it has also served to increase client awareness and expectations regarding animal care. On the legal front, it has finally given a "voice" to animals, now defined as sentient beings, thus imposing a series of duties upon veterinarians to promote their welfare. Preventing and managing pain has become a fundamental element of patient care quality in veterinary medicine, and pharmacotherapy is the basis of pain management. This paper takes this as a starting point to clarify the concept of pain in veterinary medicine and explores the relevance of an ethic to the clinical setting which gives the animal patient a strong right to freedom from unnecessary pain and thus creating moral obligations towards patients on the part of veterinary professionals. There is the duty not to inflict pain and suffering beyond what is necessary for effective diagnosis and treatment on the one hand and a duty to do all that can be done to relieve all the pain and suffering which can be alleviated on the other.