Solubilized envelope antigens (glycoproteins) of Sendai virus were purified in a DEAE-Bio-Gel A column. Monospecific antisera were prepared against the antigens, designated HN and F glycoproteins. These glycoproteins are antigenically distinct. Immunodiffusion analyses of the envelope antigens of three representative paramyxoviruses (Sendai, Yucaipa, and Newcastle disease virus) did not reveal any cross-reactions among them with antisera specific for Sendai virus glycoproteins.