The purpose of this study was the clinical and microbiological re-examination of dental hygienists, who, 30 months before, had shown remarkably high supragingival levels of periodontitis-associated micro-organisms. Interdental plaque was collected from the same molar sites and investigated by the same immunofluorescence assay with taxa-specific monoclonal antibodies as at the initial examination. On average, the 15 re-examined subjects showed slightly increased plaque levels but unchanged bleeding on probing scores (0.3-1.4). Pocket formation was restricted to a single subject. Prevotella intermedia/P. nigrescens and Peptostreptococcus micros were present in every plaque sample. Prevalences of Actinobacillus actinomycetemcomitans, Bacteroides forsythus and Campylobacter rectus were again between 20-40%, but some fluctuation within subjects was noted. The data confirm supragingival plaque as a natural habitat for periodontitis-associated bacteria in periodontially healthy persons, and indicate that colonization with A. actinomycetemcomitans, B. forsythus or C. rectus is mostly stable in spite of better than average personal plaque control.