The binding of viruses to synthetic polyacrylamide (PAA)-based sialylglycoconjugates was used to characterize the receptor specificities of antibody escape mutants of the influenza virus A/Mallard/Pennsylvania/10218/84 (H5N2). The sialylglycoconjugates that were used carried identical terminal Neu5Acalpha2-3Gal moieties but differed in the structure of the next saccharide residue(s). Our data show that mutations in the vicinity of the haemagglutinin (HA) receptor-binding site (RBS) effect the recognition of the third saccharide residue and change the affinity pattern of binding. The affinity of the majority of the escape mutants for sialyl receptors increased compared to the parental strain.