The minimum ignition energy (MIE) is an important property for designing safety standards and understanding the ignition process of combustible mixtures. Even though the formation of flame kernels in quiescent methane air mixtures has been simulated numerically, the ignition mechanism has never been satisfactorily explained. This study investigated the spark ignition of methane air mixtures through a numerical analysis using detailed chemical kinetics consisting of 53 species and 325 elementary reactions while considering the heat loss to the electrode. The simulation was used to investigate the quenching distance and the effects on the MIE of the electrode size, electrode gap distance, ignition duration, and equivalence ratio. The effect of the equivalence ratio on the ignition delay time was also examined. The simulated results showed the same trend as previous experimental results. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.