The cell-associated glycoproteins of respiratory syncytial (RS) virus included GP1 (90K), VP70 (70K), VGP48 (48K) and GP26 (26K). Although present in infected cells, there was no VP70 in purified virus. Trypsin treatment of infected cells removed 80 to 90% of VP70 as well as its products VGP48 and GP26. This suggested that most of the VP70 in the cell is located on the plasma membrane. The glycoproteins of purified RS virus (GP1, VGP48 and GP26) contain mannose, galactose and fucose as well as glucosamine, but the quantity of mannose in GP1 is low when compared to that of the other three sugars. The effects that follow the treatment of infected cells with the glycosylation inhibitors tunicamycin and monensin, and the treatment of the immunoprecipitated product of pulse-chase experiments with endonuclease H demonstrated that VP70 and its products contained N-linked oligosaccharides, and that the oligosaccharides of the mature VGP48 subunit were of the complex type, while GP1 contained both N- and O-linked oligosaccharides. The non-glycosylated forms of VP70 and GP1 have estimated mol. wt. of 50K and 33K respectively. Therefore, the carbohydrate contribution to the mol. wt. of VP70 and GP1, as determined by PAGE, was equivalent to 20K for the former and 57K for the latter. The majority of the GP1 oligosaccharides were O-linked, a form of sugar linkage not previously found among paramyxoviruses.