Two new assays have been devised to quantitate bacterial aggregating activity in human saliva. The techniques employ 3H-thymidine labeled bacteria with separation of free from aggregated cells by either filtration or centrifugation. The assays rapidly determine an early event in the aggregation of oral streptococci, allowing accurate estimates of aggregating activity in whole human saliva. We propose to further purify and characterize aggregating activity and determine the relationship of this activity to bacterial adherence. To determine the role of bacterial aggregation in oral health, we will evaluate activity and correlate this measurement with the presence of heritable polymorphic salivary proteins, nutrition and oral hygiene, DMFS, plaque and periodontal indices. The studies are designed to identify a sub set of the population at high risk for dental disease.