The role of sialic acid in the receptors for vesicular stomatitis virus (VSV) was investigated by treating chick embryo related (CER) cells and goose erythrocytes with neuraminidases from different sources and studying the effects produced on both infection and haemagglutination. The virus attachment to CER cells was reduced by their treatment with C. perfringens and A. ureafaciens neuraminidases and the susceptibility to viral infection of desialylated CER cells was recovered by coating with gangliosides immediately after enzymatic treatment. By contrast, enzymatic treatment of goose erythrocytes enhanced their agglutinability by VSV. The experiments carried out to test the ability of sialoglycolipids (gangliosides) and asialoglycolipids (cerebrosides) to inhibit virus attachment to CER cells or to goose erythrocytes showed that only gangliosides were able to inhibit VSV infection and haemagglutination.