he question of withholding treatment from a patient whose life is judged no longer valuable is most likely to arise at the endpoints of the life cycle: early infancy and old age. While active euthanasia is illegal, the decision not to treat a patient who is terminally ill or whose chances for a normal life are felt to be poor has in many instances received positive legal sanction, and sometimes religious and social endorsement as well. As a sociologist, I am interested in these decisions because they stem from the social roots of decision-makers and have consequences for society. An important question, then, is: how are such decisions made? Often cases are decided on an individual basis rather than in categorical terms-if a couple does not wish to bring its Down's syndrome baby home, they may instruct the physician not to perform intestinal surgery necessary for the child's survival. However, in the case of myelomeningocele (spina bifida), sets of guidelines have been established by physicians, so that only those children that meet certain predetermined criteria are given the surgery necessary to preserve life. What is the sociological basis for the establishment of such criteria? One way of exploring that question is to examine the physician's definition of the situation, as it derives from a more general medical world-view. The physician's view in such cases may not conform to the layman's, particularly the patient's family. The ethical implications of these differing definitions should be of concern to decisionmakers and those who guide decision-makers toward various courses of action or non-action in such cases.