Four mouse monoclonal antibodies (MoAbs)) against potato virus S Andean strain (PVSA) were tested. While MoAbs 2 and 3 reacted only with complete virions and were apparently specific for epitopes dependent on quaternary structure, MoAbs 1 and 4 appared to be conformation independent and reacted with exposed regions on native virions as well as on the surface of dissociated coat protein subunits. This seems to be an evidence of metatope existence. The results of competitive binding tests together with reaction patterns of individual MoAbs suggest that the used MoAbs reacted with at least two different epitopes on PVSA particles or polypeptide subunits. Immunoblot analysis of proteolytically cleaved PVSA capsid protein (CP) confirmed close proximity of epitopes recognized by MoAbs 1 and 4. Anti-PVS polyclonal antibody recognized both intact CP and its natural or artificial digest, while the MoAbs bound to intact CP only. These results indicate that the surface virus-specific epitopes are located near the terminus of CP molecule as it is characteristic for potyviruses.