The radio-immunoblot (RIB) assay was used to examine the antibody response to proteins of the vaccine strains induced after influenza vaccination. Vaccination stimulated an antibody response to the surface glycoproteins (HA and NA) and to the internal antigens (NP and M) of the three vaccine strains. Antibodies were detected to both the monomeric form of the haemagglutinin (HA) and its two subunits HA1 and HA2. In addition, antibody to the monomeric form of NA was detected. A wide range of response patterns was observed to the viral proteins. All three major antibody classes (IgG, IgA and IgM) were induced after vaccination and in the majority of volunteers the antibody reactivity increased one week after vaccination. IgM antibodies had a wider reactivity pattern, recognising proteins and subunits which were not fully processed or slightly degraded. The varied antibody response induced after influenza vaccination reflects the differing infection histories of the volunteers with influenza. We show some of the practical limitations of studying the antibody response to influenza vaccination.