Synthetic peptides representing regions of the VP1 protein of foot-and-mouth disease virus strain 01 Kaufbeuren were screened for their ability to stimulate proliferation of PBMC from virus vaccinated cattle. Sites were identified at residue 21-40 (peptide FMDV32) and in the region C-terminal to residue 161. Cells responding to FMDV32 were MHC class II-restricted, CD4+ and secreted IL-2. Thus, this region is defined as a Th site. Of 19 virus vaccinated Friesian cattle, 89% (17/19) responded to purified virus while 37% (7/19; 41% of virus responders) also responded to FMDV32 suggesting that this site is immunodominant for the cattle used. Furthermore, immunisation of FMDV32 responder and non-responder cattle with a related peptide, FMDV5 (FMDV32 co-linearly synthesized with the 141-160 VP1 B cell site), induced neutralizing antibody and a virus-specific T cell population in the FMDV32-responder but not the non-responder animals.