TOP/DOMDEC — A software tool for mesh partitioning and parallel processing. TOP/DOMDEC is an interactive software package for mesh partitioning and parallel processing. It offers several state-of-the-art graph decomposition algorithms in a user friendly environment. Generated mesh partitions can be smoothed and optimized for minimum interface and maximum load balance using one of several non-deterministic optimization algorithms. TOP/DOMDEC also provides real-time means for assessing a priori the quality of a mesh partition and discriminating between different partitioning algorithms. The user interface includes high speed three-dimensional graphics, an interprocessor communication simulator for today’s massively parallel systems, and an output function with parallel I/O data structures. In this paper, we describe the basic features of TOP/DOMDEC and highlight their application to the parallel solution of computational fluid and solid mechanics problems.