The primary purpose of this research project is to determine the prevalence and patterns of infection by Actinobacillus actinomycetemcomitans (Aa) and Porphyromonas gingivalis (Pg) in the general population. Antibodies to these pathogens will be measured in serum from participants ages 12 and older from the Third National Health and Nutrition Examination Survey (NHANES III), a large representative sample survey of the U.S. population. Antibody levels will then be correlated with questionnaire (sociodemographic characteristics) and examination (clinical periodontal status) data from NHANES III. A contract has been let to an external laboratory to conduct the ELISA antibody tests on the 10,000 serum samples collected during Phase II of NHANES III. This testing is using a monoclonal antibody detection system. Expert consultants in immunology and dental research are finalizing plans to quantify the measurement of antibody titer (in gravimetric units, fg/ml) and to establish a national standard serum reference (characterized and calibrated so that it can be used by the external research community). The laboratory assays should be completed by June 1998. The data will be linked to all other characteristics of NHANES III participants, including clinical indicators of periodontitis.