THE BELIEF that man's illnesses are directly and primarily attributable to some physical cause such as bacteria, virus, trauma, or changes due to deterioration was widely accepted until recently. The idea that mental or emotional factors might play a significant role was, in a large measure, disparaged. Gradually, however, the realization has developed that psychological and emotional disturbances may have a very definite place in the etiology of many illnesses. Physiologic functions and tissue reactions, it is postulated, may be produced by psychic factors. A brief review of some of the earlier investigators that have contributed to the establishment of the scientific study of these relationships is essential to an intelligent understanding of more recent trends and developments.The idea of a mind-body relationship is by no means new. It was recognized by the ancients and emphasized in their writings. Many passages in literature refer to strong emotional tension affecting the physical state. Common expressions in our everyday speech indicate an intuitive acceptance of this idea-"white with rage," "it burned me up," and the like.Delay in the scientific study of the mind-body relationship can be accounted for largely by the fact that mythology and demonology have been associated with this concept and have, as a result, produced an emotionally biased point of view and inhibited clear, critical thinking. Dissipation of this unhealthy attitude began with the era of scientific medicine. The founding of the modern schools of anatomy, bacteriology, physiology, and pathology gradually produced a clearer understanding of man as a physical organism and of some of the factors influencing his functioning. In addition, methods and procedures for scientific study have been developed. The dramatic results of these years are apparent on every hand. Yet the explanation for many illnesses remains obscure. Physical factors alone cannot account for them. Two circumstances, the large group of unexplained illnesses and the slow but persistent development toward greater understanding of mental and emotional factors as they influence man, have served to stimulate study into the possible relationship between them.This new field of interest is known as psychosomatic medicine. In essence the term connotes first, a point of view or basic philosophy in which there is no sharp cleavage between physical and psychical factors in illness; second, the giving of equal consideration in the study of illness to physical and psychical factors important in each case; and third, the belief that not only physical methods but also psychological methods of study are essential in each case.