The analysis of electrophoretic protein profiles of 21 Mobiluncus curtisii, 11 Mobiluncus mulieris and 3 reference strains (Mobiluncus curtisii subsp. curtisii ATCC 35241, Mobiluncus curtisii subsp. holmesii ATCC 35242 and Mobiluncus mulieris BV 64-5) demonstrated species-related patterns. A highly variable region appeared at 70-85 kDa for Mobiluncus curtisii and at 75-95 kDa for Mobiluncus mulieris, which was likely to correspond to cell surface located proteins. When performed under standardized conditions, PAGE-protein analysis allowed to define intraspecies clusters, from which some strains appeared identical. Thus, the method seemed to provide a useful additive to identify a strain at the species level and might be of epidemiological interest.