Two-dimensional compressible momentum and energy. equations are solved in a parallel plate channel to obtain the effect of compressibility on gaseous flow characteristics in micro-channels. The numerical methodology is based on arbitrary-Lagrangian-Eulerian method. The computations were performed for a wide range of Reynolds number and Mach number and for both 'no heat conduction' and isothermal flow conditions. The results are presented in form of the product of friction factor and Reynolds number (f . Re) expressed as a function of both Reynolds number and Mach number and was compared with available experimental results. It was found that f . Re is mainly a function of Mach number and is different from the incompressible value of 96 for parallel-plate channels. (C) 2003 Elsevier Science Ltd. All rights reserved.