Tea (Camellia sinensis) catechins have been studied for disease prevention. These compounds undergo oxidation and produce H(2)O(2). We have previously shown that holding tea solution or chewing tea leaves generates high salivary catechin levels. Herein, we examined the generation of H(2)O(2) in the oral cavity by green tea solution or leaves. Human volunteers holding green tea solution (0.1-0.6%) developed salivary H(2)O(2) with C(max) = 2.9-9.6 microM and AUC(0 --> infinity) = 8.5-285.3 microM min. Chewing 2 g green tea leaves produced higher levels of H(2)O(2) (C(max) = 31.2 microM, AUC(0 --> infinity) = 1290.9 microM min). Salivary H(2)O(2) correlated with catechin levels and with predicted levels of H(2)O(2) (C(max(expected)) = 36 microM vs C(max(determined)) = 31.2 microM). Salivary H(2)O(2) and catechin concentrations were similar to those that are biologically active in vitro. Catechin-generated H(2)O(2) may, therefore, have a role in disease prevention by green tea.