The test classically used for the serological diagnosis of yersiniosis is based on the technique of agglutination of killed bacteria. The sensitivity of this technique is low and numerous cross reactions are observed. The aim of this work was to develop a new serological test based on the ELISA method and to compare the results obtained by this method and by agglutination. The antigens used for the ELISA test were the virulence plasmid-encoded proteins present in all pathogenic Yersinia and specific for this bacterial genera. The background of this technique was determined using 30 normal human sera. Validation of the ELISA method was performed with human sera negative (23) or positive (72) by the agglutination technique. The sensitivity of the ELISA test was compared with that of agglutination using 10 patients' sera which remained negative by the agglutination test despite the isolation of a pathogenic Yersinia. Finally, the ELISA specificity was determined with the sera of patients suffering from tuberculosis (20), typhoid fever (6), suspected or confirmed brucellosis (5) and suspected yersiniosis but having a positive Wright reaction (13). We show here that, in addition to the advantages inherent in the ELISA technique, this test is more sensitive and specific than the agglutination test. Furthermore, the ELISA test can be used for all pathogenic Yersinia, whatever their serotype and biotype. The use of the ELISA test should significantly improve the serodiagnosis of yersiniosis.