The name of glycophorin was given by Marchesi et al. (1972) to the major sialoglycophorin of human erythrocyte membranes, known earlier as the glycoprotein carrying blood group M and N determinants and receptors for agglutinins of influenza viruses (Baranowski et al., 1959; Romanowska 1959; Klenk & Uhlenbruck, 1960; Kathan et al., 1961; Springer et al., 1966). Fractionation of the erythrocyte membranes by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and visualization of sialoglycoproteins with periodic acid-Schiff (PAS) reagent give a complex pattern of bands which may differ in details, depending on electro- phoretic conditions. It has been now accepted that there are at least four distinct sialoglycoproteins in human erythrocyte membranes. Furthmayr et al. (1975) designated three of them as glycophorin A, B and C, in order of their decreasing amount in the membrane. Anstee et al. (1979) denoted them glycoprotein α, β, γ and δ, in order of their decreasing molecular weight. Dahr et al. (1978c) used other designations. The more numerous bands seen in SDS-PAGE correspond to monomers of the sialoglycoproteins and to homo- and heterodimers (and higher oligomers) formed by the most abundant glycophorins A and B (Fig. 1).