New reaction mechanism has been found for the pyrolysis of anisole according to the total product analysis based on the liquid- and gas-phase H-1 and C-13 NMR spectroscopy. Formaldehyde and benzene are produced in the first rate-determining step by the intramolecular proton transfer, and phenol, methane, and carbon monoxide in equal amounts successively through the fast intermolecular proton and hydride transfers from hot formaldehyde to anisole.