In an attempt to predict some of the trends along which Clinical Investigation may proceed in the next few decades, the subject of Preventive Medicine naturally arises asa field for these ac-tivities. The term, Clinical Investigation in Prevenfive Medicine, is cumbersome and so I will not use it. In fact even the term, Preventive Medicine has never seemed ideal. It implies a little too much in the way of Propaganda. It presupposes the existence of a so-called sister science, Curative Medicine, and both sciences are com-mitted perhaps too definitely to a therapeutic program. Clinical Investigation in Epidemiology is better for the purposes at hand; Clinical Epi-demiology is best, and really what Imean. In fact this is the name I would like to propose for a new science; a new discipline in which this Society might takean important part. It is a science concerned with circumstances, whether they are" functional" or" organic," under which human disease is prone to develop. It is a science concerned with the ecology of human disease. But it is more than that, for any science worthy to be qualified by the name Clinical, should involve some attempt at the interpretation of the circumstances with which it deals. It must face the question of" why," as well as" how." Clinical Epidemiology differs, therefore, from the orthodox science of Epidemiology both in its aim, and its locale, as it were. The orthodox epidemiologist must of necessity deal dispassionately with large groups of people. It is the multiplication of observations which give him his results. The clinical epidemi-ologist, on the other hand, must ofnecessity deal with small groups of people; people whom he knows well and groups no larger than a family, or small community. The restriction of the size of the group rests on the fact that clinical judgment cannot be applied wholesale, without the risk of its being spread too thinly to be effective. For-