A brief historical account of the use of animals in research is followed by descriptions of the use of animals in modern bio-medical experiments. Emphasis is given to studies investigating the effects of radiation on animals including both somatic and genetic effects. The effects of radiation in the environment are studied by analyzing animals for traces of radioactive isotopes, determining the effects of reactor operations on birds and studying wasps nesting near a radioactive waste disposal pond. Studies with animals enabled establishment of safety standards for humans exposed to radiation. Applied uses of radiation in medicine, veterinary medicine, and insect control are described. Details of the care, use, and production of laboratory animals are given. The first appendix gives a census of laboratory animals used by the Atomic Energy Commission and the second lists guiding principles for the use of animals by secondary school students. Suggested references and a film list are included. (AL)