In modeling a rapid compression machine (RCM) experiment, it zero-dimensional code is commonly Used along, with all associated heat loss model. However, the applicability of Such a zero-dimensional modeling, needs to be assessed over a range,e of accessible experimental conditions. It is expected that when there exists significant influence the dimensional effects. including boundary layer, vortex roll-up and nonuniform heat release. the zero-dimensional modeling may not be adequate. In this work. We Simulate ignition of hydrogen in in RCM by employing computational fluid dynamics (CFD) studies with detailed chemistry. Through the comparison of CFD simulations with zero-dimensional results. the validity of zero-dimensional modeling for simulating RCM experiments is assessed. Results show that the zero-dimensional modeling based oil the approach of "adiabatic volume expansion" generally performs very well in adequately predicting the ,ignition delay of hydrogen. especially when a well-defined homogenous, core is retained within all RCM. As expected, the performance of this zero-dimensional modeling deteriorates with increasing temperature nonuniformity within the reaction chamber. Implications for the species sampling experiments in all RCM Lire further discussed. Proper interpretation of the measured species concentrations is emphasized and the validity of stimulating RCM species sampling results With a zero-dimensional model is assessed. (C) 2008 The Combustion Institute. Published by Elsevier Inc. All rights reserved.