The sites of linear epitopes in a variable region of the attachment (G) glycoprotein of respiratory syncytial virus (RSV) that are recognised by the human antibody response were examined. Two sets of overlapping 12mer peptides each representing the carboxy-terminal 84 or 85 amino acids of the G protein of two group A isolates of human RSV were synthesised. These peptides were analysed using enzyme-linked immunosorbant assays (ELISA) for their reactions with sera obtained from infants with primary RSV infection. Four pairs of overlapping peptides were found to react variously with the sera, the reactions depending on the infecting genotype of RSV. Further 9mer peptides based on natural variants in the epitope areas were then synthesised to determine the specificity of the human antibody response and it was found that single amino acid changes could abrogate recognition by these polyclonal sera. All the linear epitopes found are involved in potential N-glycosylation sites in at least some isolates of RSV.