Domain decomposition strategies and computational mesh reordering are discussed for finite difference parallel simulations of groundwater contaminants transport. The parallel performance of point iterative methods traditionally used in groundwater pollution modelling is studied. The algorithms were implemented with red-black and wavefront reordering of the computational mesh. A standard conservative transport equation defined on a two-dimensional grid with Dirichlet boundary conditions was used for the analysis. Completely portable multiple instructions multiple data (MIMD) implementations of the algorithm were performed using message-passing interface (MPI). The runtimes of the algorithms are presented as a function of grid refinement and number of processors, and the communication overhead of the parallel simulation process is investigated, showing that the red-black reordering technique yields the best performance results. The method also provides higher efficiency and scalability when applied to large-scale problems. Optimal parameters are suggested for parallel simulation of groundwater pollution using finite difference schemes. © Elsevier Science Inc., 1998.