The purpose of this work has been experimental measurement of the rate of formation of nitric oxide in combustion processes occuring under conditions similar to those found in practice. At the same time, development of a reaction mechanism and chemical kinetic calculation technique capable of accurately predicting formation rates of nitric oxide has been attempted. Ultraviolet absorption techniques were used to directly record the time rate of formation of nitric oxide in the immediate vicinity of a flame front propagating through a high pressure combustion vessel. Hydrogen and propane were used as fuels. The oxidizer was air or air diluted with nitrogen.