Monoclonal antibodies to Ogawa-Inaba common antigenic determinant and Ogawa specific antigenic determinant of V. cholerae belonging to the serogroup O1 were generated from BALB/c mice immunized with V. cholerae O1 Eltor Ogawa strain. Reactivity and specificities of the monoclonal antibodies were examined by slide agglutination method. The monoclonal antibodies agglutinated all the V. cholerae O1 strains tested but did not agglutinate with any of the other currently recognized 140 serogroups of V. cholerae non-O1 as well as with a variety of other enteric pathogens. Diagnostic utility of the MAbs produced in this study as compared to polyclonal O1 and monospecific antisera showed that the MAbs were as good as the latter for serological diagnosis of the two serotypes of V. cholerae O1.