Abstract
Viruses producing an unusual "sponge-like" cytopathogenic change in monkey kidney tissue culture were isolated from the pharyngeal swabs of 2 of 12 infants with croup. The infants from whom the viruses were isolated and 3 additional patients developed significant increases in neutralizing or hemagglutination-inhibition and complement-fixing or all 3 varieties of antibody during convalescence. The isolated agents appeared to be similar antigenically.