Peptides representing the sequence of the immunodominant loop of foot-and-mouth disease virus strain C-S8 (YTASARGDLAHLTTTHARHLP, residues 136-156 of VP1) and of several variant viruses have been prepared by solid phase methods. In addition, five peptides with single-residue replacements at Leu147 (Ile, Nle, Val, Ala, Gly) have been synthesized. Tosyl and dinitrophenyl protections for histidine have been compared, the latter being found to give better synthetic products. The peptides have been tested in an immunodot assay against a panel of monoclonal antibodies directed towards the VP1 loop. Immunochemical results are discussed on the basis of the mobility of the region reproduced by the peptides and the nature of the side chain of residue 147.