Herpesvirus papio 2 (HVP2), which infects baboons, is much more closely related genetically and antigenically to monkey B virus (BV) than to human herpes simplex virus 1(HSV1) and other related herpes viruses. The usefulness of HVP2 as an alternative test antigen in immunoblotting assays to detect BV-antibody in macaque monkey sera was assessed. Six HVP2 proteins reacted with BV-positive sera in immunoblotting. No specific bands could be detected with BV-negative sera. These results show the usefulness of HVP2 antigen as an alternative and safer antigen than authentic BV antigen in detecting BV antibody in immunoblotting.