Objective: To define and compare the microbiologic profile of subgingival plaque in German patients with periodontitis (including aggressive and advanced chronic periodontitis) and healthy subjects and to determine significant association between isolates and clinical status. Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and Tannerella forsythia are major periodontal pathogens, though it is recognized that other species may also contribute to the pathogenesis of periodontal disease. Method and Materials: Thirty-three patients with clinical and radiologic proof of aggressive and advanced chronic periodontitis and 20 healthy subjects were enrolled in this study. Clinical indices were recorded as six-point measurements on each tooth. Samples of the subgingival plaque were taken with paper points from four teeth of each individual. The samples were divided into two parts. One part was immediately cultivated, while the other one was stored at -20°C until analyzed by real-time polymerase chain reaction. Results: A total of 284 anaerobic isolates (224 isolates from patients and 60 isolates from healthy controls) were identified. Forty different anaerobic species were isolated, with a mean of 6.78 species per patient and 3 species per healthy control subject. Significant differences in prevalence (after adjusting for multiple comparisons, P .001) were found for Prevotella intermedia/nigrescens, Fusobacterium nucleatum, T forsythia, Treponema denticola, and Veillonella parvula. The first four species were associated with the aggressive periodontitis group and V parvula with healthy subjects. Conclusion: When compared with healthy controls, the microbial profile of subgingival plaque from periodontitis was found to contain known periodontal pathogens with a different prevalence to that described in earlier studies. P intermedia/nigrescens, F nucleatum, T forsythia, and T denticola have been found in lower proportions and small quantities in healthy subjects. Keywords: periodontal pathogens, periodontitis, subgingival plaque