A study of gaseous fuel/air mixing in a simplified two-dimensional axisymetrical cylinder shaped chamber with centrally located orifice inlet condition is performed using multi-dimensional computational fluid dynamic analysis. The gaseous fuel concentration distribution formed by in-cylinder charge motion is also predicted. The effect of swirl on global mixing is examined. and the optimal swirl is determined for a particular value of engine speed. A measure of global uniformity is defined and used to gain information about the fuel concentration distribution Within the chamber. The computational results show that the flow field has a great effect on charge mixing. The charge mixing is satisfactorily close to the desirable mixing distribution When the fuel charge is prescribed property. Copyright (C) 2003 John Wiley Sons. Ltd.