Lawrence J. Prograis Jr., MD, is senior scientist, Special Programs and Bioethics, Division of Allergy, Immunology and Transplantation at the National Institute of Allergy and Infectious Diseases, the National Institutes of Health. Edmund D. Pellegrino, MD, is the John Carroll Professor of Medicine and Medical Ethics Emeritus at Georgetown University. He is the coeditor of Jewish and Catholic Bioethics.