We report the localization of three monoclonal antibody (MAb) binding sites in the capsid protein of feline calicivirus. Gene fragments were generated by restriction enzyme digestion or the polymerase chain reaction, and expressed as beta-galactosidase fusion proteins in Escherichia coli. These chimeric molecules were screened using three MAbs. A non-neutralizing MAb recognized a region within 36 amino acids of the C terminus. Two neutralizing MAbs bound to a different region of 37 amino acids in the centre of the protein. Comparative sequence analysis shows this area to be the major variable region of the capsid protein.