Green tea catechins with the anticariogenic activity have been recently revealed to maintain their salivary concentrations after mouthrinsing. The mechanism underlying such retention in the oral cavity was studied by quantitatively evaluating the adsorption of catechins after vortex-mixing with hydroxyapatite, buccal mucosal cells, and proteins in artificial saliva. Treatment with hydroxyapatite decreased catechins in supernatants and such a decrease was more significant by coating hydroxyapatite with saliva as an experimental pellicle. When treating with mucosal cells, unwashed cells decreased catechins in ultrafiltrates more significantly than washed cells. Catechins in ultrafiltrates were decreased by treating with albumin and mucin depending on protein concentrations. These reduced concentrations in supernatants and ultrafiltrates meant the adsorption of catechins to hydroxyapatite, mucosal cells, and proteins. In structural comparison, four gallate esters were superior in the adsorptive activity to the corresponding non-esters. Concentration changes of salivary ctechins after mouthrinsing with green tea extracts showed that the retention of catechins in the oral cavity was associated with their adsorption. The present results suggested that green tea catechins are adsorbed by the teeth, pellicles and oral mucosa, and that salivary proteins such as albumin and mucin are responsible for the adsorption. The adsorbed catechins are considered to gradually be released to maintain the salivary concentrations after oral application.