A highly sensitive, effective and rapid method--a competitive alternative to ELISA--was developed for the detection of specific antibodies to Y. pseudotuberculosis. It is based on monoclonal antibodies (MAbs) recognizing the species- or serogroup specific epitopes of Y. pseudotuberculosis. The competitive ELISA was used in testing the murine hyperimmune sera and human antisera sampled from patients with different infectious intestinal diseases including several cases of pseudotuberculosis. The use of the MAbs-based ELISA in the laboratory diagnostics of pseudotuberculosis is under discussion.