This issue of ILAR Journal begins with ethical history, proceeds to contemporary ethical theories, and concludes with practical applications of the ethics of animal research. The editors recognize that one issue of one journal cannot do full justice to the growing discipline of biomedical ethics concerning laboratory animals. We hope, however, that the issue will provide thoughtful readers with a basis for creating, embracing, or enriching the moral framework that governs their attitudes and behavior toward laboratory animals. The second half of the 20th century has been a time when biomedical ethics has burgeoned, unlike any time since the creation of the university as an institution in the 13th century. It is not difficult to understand why the field of biomedical ethics has taken a central place in philosophy departments, medical schools, and science departments throughout the United States and western Europe. The dramatic advances of the biological sciences, and the equally dramatic growth of science-based technology, have raised critical problems that were previously considered to be hypothetical, while providing new urgency to the resolution of old problems. Consider for a moment that combined public and private funds support more than $40 billion worth of biomedical research each year. For more than 50 yr, our country has generated more heat than light in clarifying the rights and wrongs of abortion. We seem to be no closer to a national consensus on that issue than we were when it was settled in Roe versus Wade. Problems that range from the moral propriety of fetal research, human in vitro fertilization, and the use of fertility drugs are addressed by the public in general and by trained ethicists in particular. The permissibility of research involving cognitively impaired patients challenges our society and the National Bioethics Advisory Commission. Altering human genetic codes, gene splicing, organ procurement and transplantation, advance directives governing the limits to treatment or the conditions under which an incompetent person may be involved as a research subject provide complex and vexing moral as well as scientific questions. Issuing DO NOT RESUSCITATE orders, controlling intractable pain by administering life-threatening doses of morphine or other palliative drugs, advance directives, health care managed by insurance companies, the validity of a right to minimal health care, and many other questions have occupied the attention of a new breed of bioethicists who seek to provide a rationale for moral decision making in these and many other situations. Perhaps no issue, with the exception of the abortion question, has generated more heated controversy than the appropriate use of laboratory animals. At the extreme, persons opposed to the use of animals in research have resorted to civil disobedience and physical violence to draw attention to their views. Although polls reveal that nearly 80% of the general public endorse the use of animals in research, that endorsement is conditioned on humane care and use of the animals. Consequently, the care and use of laboratory animals is among the most strictly regulated industries in the country, ranking close behind air traffic safety and the manufacture of safe drugs, devices, biologies, and food products. It is surprising, therefore, to realize that there is at present