Domain partitioning is a widely-used approach in parallel implementation on MIMD computers. In this paper, we propose a new parallel SOR method, the PSOR method, formulated by using domain Partitioning together with an interprocessor data-communication technique. We prove that the PSOR method can have the same asymptotic rate of convergence as the corresponding sequential SOR method. We also demonstrate the parallel performance of the PSOR method on a shared memory MIMD computer (a KSR1) and three distributed memory MIMD computers (the Intel Delta, an Intel Paragon L38 and an IBM POWERparallel System 9076 SP2).