Previous studies have revealed a similarity between hemadsorption and bacterial adherence to virus-infected cells. This observation led to the question of whether mature virions can interact directly with bacteria in a manner similar to hemagglutination. Thus, hemagglutination inhibition, direct immunofluorescence, and scanning electron microscopy were used to detect adherence of five prototype strains of influenza A virus to 34 strains (five serologic prototypes and 29 isolates from ill infants) of group B Streptococcus. Group B Streptococcus serotypes Ia, Ic, and III appear to possess receptors for the five influenza strains that are sensitive to receptor-destroying enzyme. The results of adherence tests with Streptococcus serotype Ib depended on which bacterial strain was used. Only one virus prototype, Jap/305/57(H2N2), adhered to all of the 34 strains of Streptococcus tested.