Competitive binding studies and antigen capture assays were done with monoclonal antibodies (MAbs) raised against hog cholera virus (HCV) to map the corresponding epitopes. A model was constructed in which the 13 epitopes were situated in four distinct antigenic domains: A, B, C and D. Domain A was subdivided into A1, A2 and A3. The functional relevance of this model was assessed by the characterization of pestivirus strains, by neutralization studies with the MAbs, and by isolation of variants that escaped neutralization. The topographical arrangement of the epitopes, as constructed in the model, was corroborated by the functional assays. The MAbs that defined domains A1 and A2 recognized all 94 HCV strains tested. Domains A3, B, C and D varied among the HCV strains. Neutralization was observed with MAbs defining domains A1, B and C. Synergistic neutralization occurred using MAbs against domains A1 and B, and A1 and C, but not within the domains. With MAbs defining A1, B or C, variants could be isolated that escaped neutralization and immunostaining by these MAbs.