A shock tube technique was employed to study the fast pyrolysis of cellulose with methane under conditions of high temperature, high heating rate, short reaction time, and rapid quenching. The effects of temperature, methane atmosphere, and reaction time are investigated. Experiments were carried out at temperatures between 700 and 2200-degrees-C in 1% methane (diluted in argon), and comparisons in the yields of major gas products are made with the results obtained in pure argon atmosphere. The total gas yield decreased about 25-30% in methane. The principal gas products-carbon monoxide, carbon dioxide, and acetylene, except ethylene-were significantly decreased in methane as compared to the yields in pure argon. An increase of about 25% in ethylene yield in methane over argon was observed. The onset of the decomposition of cellulose and the evolution of major pyrolysis products were changed with the reaction times, which also affected the amplitude and the distribution of the pyrolysis products.