The purpose of this project is to investigate the interactions of saliva and specific salivary proteins with oral bacteria and bacterial enzymes/products involved in colonization. The coating of hydroxylapatite, glass or plastic surfaces with human saliva reduced the adherence of S. mutans to a much greater extent than of S. sanguis. However, when S. mutans were allowed to grow and form glucan in the presence of sucrose the bacteria adhered as well to saliva-coated as to uncoated surfaces. An enhanced adherence of S. sanguis was not observed under the same conditions. IgA antibodies to glucosyltransferase (GTF) and glucan of S. mutans were measured in saliva from several different human subjects. The antibody levels appeared to be inversely related to GTF activity in the saliva. Functional inhibitory antibody to GTF was not detected in any of the saliva even after inactivation of endogenous GTF activity. IgA, IgG, albumin, lysozyme, Alpha-amylase and heat-stable, acidic protein were adsorbed from human saliva by hydroxylapatite powder. Studies on the influence of these and other proteins present in saliva on factors involved in the colonization of oral streptococci are in progress.