Seven monoclonal antibodies (MAb) against the capsid protein of type 2 porcine circovirus (PCV2) were used to map the antigenic sites using PCV2 infectious DNA clones containing PCV1/PCV2- open reading frame (ORF) 2 chimeras. The chimeric PCV1/PCV2-ORF2 cassettes were constructed, by serial deletions of the PCV2-ORF2 and substitution of the deletions with the corresponding sequences of the PCV1-ORF2. The viability of the chimeras in transfected PK-15 cells was confined with a convalescent PCV2 swine antiserum. The chimeric PCV1/PCV2 clones were transfected into PK-15 cells, and their reactivities with the seven MAbs were detected by immunofluorescent assay (IFA). The chimera with a deletion of 47 amino acids at the N-terminus of PCV2-ORF2 (chimera r140) reacted strongly to all seven MAbs. Expanding the deletion of PCV2-ORF2 from amino acid residues 47 to 57 (r175) abolished the recognition of MAbs 3B7, 3C11, 4A10, 6H2 and 8F6 to the chimera. Further deletion of PCV2-ORF2 to 62 residues disrupted the binding of this chimera to all seven MAbs. Reactivities with all MAbs were absent, when amino acid residues 165-233 at the C-terminus of ORF2 was replaced with the corresponding PCV1-ORF2 sequence. Extending the sequence of PCV2-ORF2 from residues 165 (r464) to 185 (r526), 200 (r588) or 224 (r652) restored the ability of the three chimeras to bind MAbs 3C11, 6H2, 9H7 and 12G3 but not MAbs 8F6, 3B7, or 4A10. When the four amino acids at the C termini of r588 were replaced with that of PCV2-ORF2, the resulting chimera (r588F) reacted with all seven MAbs. The results from this study suggest that these seven MAbs recognized at least five different but overlapping epitopes within residues 47 to 63, 165 to 200 and the last four amino acids at the C-terminus of the PCV2 capsid protein. These epitopes are likely conformational epitopes on the exterior surface of the capsid protein.