In order to obtain optimal bovine respiratory syncytial virus adsorption to host cells, the effect of several products (fetal bovine serum, bovine serum albumin, ovalbumin and cytochrome c) was studied. The adsorption of the virus to MDBK cells was higher in the presence of 2% than in the presence of 5% fetal bovine serum. Adsorption was inhibited in the presence of bovine serum albumin at concentrations > 0.2% when added before or at the same time as the virus. Ovalbumin and cytochrome c did not inhibit adsorption. These results will allow the study of virus adsorption on cell receptors.