Standard textbooks of medicine supply excellent articles on recognized diseases, but with rare exceptions the discussions fail to include one feature of paramount importance. No mention is made of the need for explaining to the patient the nature of his problem, the mechanism and significance of his symptoms, and the course the illness may be expected to follow. This omission is unfortunate because, with present-day concentration on pathologic physiology in our medical schools, the subject also receives little or no attention in clinical teaching. As a consequence it may be several years after graduation before a young internist appreciates all that can be accomplished by sufficiently detailed instruction of those under his care. There are two principal reasons why an explanation along the lines indicated is indispensable. In the first place, it is, in many illnesses, a therapeutic tool of basic importance. Secondly, it is one of the best available