Book excerpt: Studies were conducted to finalize a fundamental and predictive reaction model for the combustion of hydrogen and carbon monoxide through a multi-parameter optimization. These studies showed that reliable data of hydrogen and carbon monoxide oxidation at high temperatures can be reconciled be a single kinetic model. An advanced approach to solve the master equation of collision energy transfer was developed to predict the rate constants of combustion reactions of arbitrary complexities. Studies were also conducted on a class of unique combustion reactions that involve spin state crossing-one of the last few unresolved theoretical problems in combustion reaction kinetics.