Experimental batches of adsorbed subunit influenza vaccine were prepared from the envelope of glycoprotein antigens separated from the influenza virion by treatment with a cationic detergent (cetyltrimethylammonium bromide). Purified and concentrated influenza virus strains A(H1N1) and A(H3N2) were obtained by gradient centrifugation; additional purification, with a view to removing ovalbumin and structural components of the chorioallantoic membrane, was achieved by gelfiltration. The composition and biological properties of the vaccine are described.