Autoignition of methylcyclohexane (MCH) is investigated in a rapid compression machine (RCM). Experiments are conducted for homogeneous MCH/O-2/N-2/Ar mixtures with equivalence ratios varying from 0.5 to 1.5, at compressed charge pressures of 15.1 and 25.5 bar, and over a compressed gas temperature range of 680-905 K. In the RCM experiments, the mole percentage of MCH is kept constant at 1.047%, while the equivalence ratio is varied through variation in oxygen mole percentage. Ignition delay measurements demonstrate the features of two-stage ignition characteristics and strong negative temperature coefficient (NTC) behavior. The NTC behavior is also noted to shift to higher temperatures at higher pressures and for oxygen-rich mixtures. In addition, both the first-stage and total ignition delays show significant dependence on oxygen mole fraction. Furthermore, the current ignition delay measurements provide additional benchmark data for the validation of the oxidation kinetics of MCH. Comparison of the experimental ignition delays with the simulated results using an available detailed kinetic mechanism is conducted and discussed. (C) 2009 The Combustion Institute. Published by Elsevier Inc. All rights reserved.