Demands on physicians and other professionally trained persons are further intensified by what might be called our system of crisis medicine. It is a system that demands superb skills. advanced knowledge and training. and excellent facilities for the care of the sick. but it is a system designed for maximum effectiveness at a time of emergency: illness or accident. For many of the very poorthe slum dweller. the migrant worker. the elderly pensioner--our advanced medical system might as well have been on another planet. In a nation now committed to delivery of best possible health care to all citizens. obviously much more must yet be done. If we are to improve dramatically the health and the health care of our Nation. there is one simple fundamental step we can take: a concentrated effort at the early detection in order to help prevent the onset of serious illness and the reduction of its severity.