Questions concerning the ethics of animal use in research and teaching have been debated by scientists, theologians, philosophers and the lay public since the use of animals for these purposes began. Even when consideration is restricted to recent discussions of the issue, there are almost as many ethical positions as there are writers on the subject. The prevailing view is that animals can and should be used in research which benefits humans and the ecosystems provided there is no acceptable alternative to such use. Implicit in this view is the expectation that research animals will be treated humanely. Extreme views are held by small minorities. On the one hand are those who believe that humans have no responsibility to other animals and, therefore, any use of animals is permissible. On the other hand are those who believe that all animals, human and non-human, have the same rights and, therefore, humans have no right to use animals for any purpose. There are many variants of each of these views and even among those who hold that animals have legal rights there is disagreement about whether all species should be accorded the same moral or legal status.

Following the prevailing view, laws and regulations at many levels require the humane treatment of animals used in research and teaching. Essential elements of humane treatment include that animals be housed in clean, comfortable quarters, that they be fed an adequate diet, and that they be maintained in good health. There is no general agreement as to what additional factors might be necessary for humane treatment. Most conscientious researchers and the agencies which regulate animal care accept that an animal's well-being is dependent on its mental state as well as its physical state. It is also recognized, however, that it is much more difficult to establish objective guidelines for the assessment of the psychological well-being of an animal than it is to monitor physical well-being.