Neutralization of human respiratory syncytial virus (HRSV) by monoclonal antibodies specific for the G protein was evaluated in a microneutralization test. Only certain antibodies showed some degree of neutralization, reflected in a reduction of virus titre (10-20 times maximum), compared with negative controls. In contrast, a pool of antibodies that recognized conserved, group-specific and strain-specific epitopes showed a significant increase in virus neutralization (up to 500-1000 times). By testing binary, tertiary and quaternary combinations, four antibodies were identified which showed maximal effect in the neutralization test. These findings are discussed in terms of the location of antibody binding sites in the G protein primary structure and their relevance for HRSV neutralization and immunobiology.