COXSACKIE GROUP A viruses have been associated with a number of clinical syndromes including aseptic meningitis,1herpangina,2and acute exanthemata.3However, little is presently known concerning the role of these agents in the pathogenesis of acute undifferentiated respiratory disease. Acquisition of such information has been hampered by the need for large numbers of suckling mice in attempts to isolate most of the members of this virus group. Several Coxsackie A viruses, however, have been recovered in tissue culture.3-5To this list has recently been added Type 21 virus, shown to be serologically indistinguishable from Coe virus originally described by Lennette et al.6 In the fall of 1960 during the course of a continuing study of acute respiratory disease in a military population, an outbreak of infection by Coxsackie A-21 virus was observed. The preceding paper7described infection and respiratory illness among a group of