Binding patterns of monoclonal IgM anti‐B, anti‐H and anti‐(Leb + Y) antibodies on erythrocytes were visualized in the backscatter electron imaging (BEI) mode of a scanning electron microscope by indirect immunogold labelling. The results were independent of secretor status, supporting the view that type 2 oligosaccharides predominate on erythrocytes. There were considerable cell‐to‐cell variations of amounts of the antigens, presumably because of differences of antigen development. The amount of H antigens may have been overestimated in previous studies. B and H antigens seemed linked mostly to mobile structures, probably lipid, on the convex parts of the cells and to immobile structures, probably protein, on the concave parts. Y antigens appeared bound to mobile structures also on the concave part of the cell membrane. The results therefore confirm that B oligosaccharides on erythrocytes develop from both lipid‐ and protein‐bound H, but suggest that Y develops mainly from lipid‐bound H.