Introduction This presentation will consider primarily the pathogenic aspects of measles. No attempt will be made to discuss in any detail the clinical features of the disease, except as they relate to our basic theme. The purpose of including such a topic on the program of this conference is that from a knowledge of the sequence of events in the natural infection it is possible to understand better the disease we seek to control and thus to plan more intelligently to do so. Your attention is called to the comprehensive review on the pathogenesis of measles by Grist in 1950.1In spite of the lapse of 11 years it is difficult to improve greatly upon his presentation. Unfortunately, many of the facts necessary to construct a well-documented picture of the pathogenesis of measles are still lacking. However, an attempt will be made to fit the available data into the