The etiology of acute respiratory infections of childhood and infancy often remains obscure. Progress has been made, however, in the classification of these illnesses by the recent discovery of a new group of viruses, subdivided into distinct serotypes, which are now referred to as adenoviruses,1 formerly the APC,2 RI,3 or ARD4 groups. Adenoviruses have been shown to be a cause of undifferentiated acute respiratory disease, nonstreptococcal exudative pharyngitis, and primary atypical pneumonia. They were also found to be associated with a clinical entity designated pharyngoconjunctival fever, which may assume epidemic proportions.3-8 Other illnesses have been ascribed to these agents which include epidemic keratoconjunctivitis9,10 and mesenteric lymphadenitis,11 and a Type 3 of these agents has been isolated from a stool of an infant with a disease resembling roseola infantum.12 While in general the diseases induced appear to be relatively mild, adenoviruses have been isolated from the lungs of two fatal cases