The resources for medical care are clearly finite, but demands on those resources are growing rapidly. Of particular concern are the demands on those resources for medical practices of three kinds: those that pose conflicts between the interests of the individual and those of society; those of no value or of undetermined value; and those for potentially preventable conditions. Such practices must be evaluated in terms of social and medical priorities, and this requirement will become more urgent with the establishment of national health insurance. Who will make decisions is less clear, but it is not likely to be physicians alone. It is imperative that physicians and other health providers work closely with professionals from many fields, and with consumers, to ensure the availability and dissemination of information that will permit decisions that are in the best interests of society.