A chemical kinetic model for high-pressure combustion of H 2=O2 mixtures has ben developed by updating some of the rate constants important under high-pressure conditions without any diluent. The revised mechanism is validated against experimental shock-tube ignition delay times and laminar flame speeds. Predictions of the present model are also compared with those by several other kinetic models proposed recently. Although predictions of those models (including the present model) agree quite well with each other and with the experimental data of ignition delay times and flame speeds at pressures lower than 10 atm, substantial differences are observed between recent experimental data of high-pressure mass burning rates and model predictions, as well as among the model predictions themselves. Different pressure dependencies of mass burning rates above 10 atm in different kinetic models result from using different rate constants in these models for HO 2 reactions, especially for H + HO2 and OH + HO 2 reactions. The rate constants for the reaction H + HO2 involving different product channels were found to be very important for the prediction of high-pressure combustion characteristics. An updated choice of rate constants for those reactions is presented on the basis of recent experimental and theoretical studies. The role of O(1D), which can be produced by the H + HO2 reaction, in the high-pressure combustion of H2 is discussed.