The use of overlapping 15mer synthetic peptides, covering the whole open reading frame of FMDV strain OX in a peptide ELISA, allowed the identification of 12 FMDV strain OX-specific linear B-cell epitopes. Six of these linear B-cell epitopes, located in the nonstructural proteins were used in further assays to compare the reactivity of sera from vaccinated and infected cattle. Antibodies recognizing these peptides could be detected only in sera derived from infected cattle. In further experiments the reactivity of the six peptides with sera from animals infected with different strains of FMDV was tested and strain independent infection-specific epitopes were identified. These results clearly demonstrate a simple peptide-based assay to discriminate between infected and conventionally FMD-vaccinated animals.