The ability of exogenous S. mutans to implant and be retained in dental plaque and saliva varied considerably among eight human subjects. To determine whether a correlation might exist between host saliva and S. mutans implantation, the effects of the different salivas on the properties of bacterial growth, aggregation, adsorption to hydroxylapatite (HA) surfaces and sucrose mediated adherence of cells to glass were assessed. Significant differences in growth and sucrose mediated adherence were not seen with the salivas tested. The degree of aggregation and the amount of adsorption to hydroxylapatite of S. mutants differed for all salivas tested. Salivas from 2 of 3 subjects that resisted implantation of S. mutans appeared to show greatest aggregation activity and to support the adsorption of the greatest number of bacteria to hydroxylapatite. All experiments have been repeated and the results are being analyzed.