A comprehensive reaction mechanism for the oxidation of carbon monoxide in the presence of hydrogen is described. Model predictions are compared with experimental data over wide ranges of physical conditions. The data, obtained from shock tube experiments and various types of reactor experiments, encompassed a combined temperature range of 823-2870 K, fuel-oxidizer equivalence ratios between 0.0005 and 6.0, C/H ratios between 0005 and 128, and pressures between 0.3 and 2.2 atmospheres, Validation of the reaction mechanism is obtained with reproduction of the experimental results by the model predictions and from sensitivity analysis calculations Results from the latter calculations provided a quantitative measure of the sensitivity of the model predictions to the imposed input parameters over the complete range of experimental parameters noted above.