KIE: The authors urge American physicians and scientists to undertake a primary role in defending the use of animals in biomedical research against a strategy of progressively more restrictive legislation and regulation initiated by determined and well-financed opponents. They argue that medical progress may be impeded by the objectives of both those who seek only more humane treatment of an absolute minimum of research animals and those whose belief in animals' moral rights precludes all use of animals. Smith and Hendee maintain that the greatest danger to animal research is not the activities of its opponents but the inactivity of its defenders in presenting their arguments to legislators and the public. They appeal for an aggressive, organized campaign by the biomedical community not only at the national level but by local professional groups and individuals at the state and county level.