The antigenic profile of 30 vaginal isolates of Mobiluncus strains (22 M. curtisii and 8 M. mulieris) was determined by immunoblotting technique using mouse immune ascitic fluids containing polyclonal antibodies against the type strains M. curtisii subsp. holmesii (ATCC 35242) and M. mulieris (ATCC 35243). Two antigenic profiles were identified within M. curtisii isolates, whereas a certain variability was observed among M. mulieris strains where at least three antigens were constantly recognized. The detection of antigenic profiles of Mobiluncus strains by immunoblotting technique provided a simple method to identify Mobiluncus isolates at the species level.