Introduction: MX virus is a recently characterized Snow Mountain virus-like human calicivirus (HuCV) identified in stool from a Mexican child with acute gastroenteritis. The expression of the recombinant MX(rMX) capsid in baculovirus permitted the development of antigen and antibody EIAs that can be used for identification of this strain.Aim: This study describes the characterization of monoclonal antibodies (Mabs) developed against the rMX antigen.Methods: Ten Mabs to the MX virus were generated using the baculovirus-expressed rMX viral capsid as immunogen. Specificity was demonstrated by immunoprecipitation and Western blot. Enzyme immune assays(EIAs) using the Mabs were used to detect MX antigens in stools.Results: Each of the Mabs reacted with the rMX antigen and with stool specimens from 5 children infected with the MX virus, but not with the baculovirus-expressed recombinant Norwalk virus capsid. The Mabs divided into 3 groups based upon cross-reactivities in a competition EIA. Each group also revealed an unique antigen binding pattern in the immunoprecipitation and Western blot analyses. EIAs utilizing the Mabs as coating or detector antibodies were specific and sensitive for detection of MX antigens in human stools. Conclusion: The unlimited supply of the rMX Mabs will allow development of type-specific assays for clinical diagnosis as well as antigenic characterization of HuCVs.