Methane pyrolysis and oxidation were studied behind reflected shock waves in the temperature range 1350-2400 It at pressures of 1.6 to 4.4 atm. Methane decay in both the pyrolysis and oxidation reactions was measured by using time-resolved infrared (IR) laser absorption at 3.39 mu m. CO2 production was also measured by time-resolved IR emission at 4.24 mu m. The production yields were also studied using a single-pulse method. The pyrolysis and oxidation of methane were modeled using a kinetic reaction mechanism including the most recent mechanism for formaldehyde, ketene, acetylene, ethylene, and ethane oxidations. The present and earlier shock tube data is reproduced by the proposed mechanism with 157 reaction steps and 48 species. The reactions and the rate constants, which were important to predict our and earlier shock tube data for methane pyrolysis and the oxidation with mixtures of wide composition from methane-rich to methane-lean, are discussed In detail.