FOUR YEARS ago at a combined meeting of the Epidemiology and Laboratory Sections of the American Public Health Association, there was a discussion of recent data pertaining to a newly isolated group of viruses, alluded to then by a variety of names, but now called adenoviruses.1 The papers presented centered about means for classification of the newly discoverea viruses, the diseases which they probably cause, and their possible importance as etiologic agents of acute respiratory infections.2-4 The intervening years have allowed time for many investigators to gather data which bear upon the points discussed with uncertainty at that time and to permit a perspective to be gained on the role of the adenoviruses as agents of disease. This paper will attempt to review some of the pertinent information obtained in the past four years and to interpret these data relative to what we may term the natural history of adenovirus infections.