A parallel DSMC method based on a cell-based data structure is developed for the efficient simulation of rarefied gas flows on PC-clusters. Parallel computation is made by decomposing the computational domain into several subdomains. Dynamic load balancing between processors is achieved based on the number of simulation particles and the number of cells allocated in each subdomain. Adjustment of cell size is also made through mesh adaptation for the improvement of solution accuracy and the efficient usage of meshes. Applications were made for a two-dimensional supersonic leading-edge flow, the axi-symmetric Rothe's nozzle, and the open hollow cylinder flare flow for validation. It was found that the present method is an efficient tool for the simulation of rarefied gas flows on PC-based parallel machines. Copyright (C) 2004 John Wiley Sons, Ltd.