Abstract
We have set a high standard of evidence for the evaluation of preventive services to be widely used. Cost is one reason. Since everyone is a candidate for preventive services, the aggregate cost is high. Professional ethics is another reason. By seeking out a physician, a sick patient initiates an episode of care. The physician's responsibility is to help, not to guarantee a good outcome. The obligation is more stringent when a physician makes a recommendation to a healthy person: the physician must be sure that the benefits exceed the harm (primum non nocere). For example, screening for a disease . . .