Monte Carlo simulations are a powerful tool in statistical mechanics and particle physics. In the latter field they are the leading technique for computing experimental properties of strongly interacting particles from first principles in quantum chromodynamics (QCD). However, due to their enormous demand on compute: power, these simulations remain a challenge to both physicists and computer scientists. To overcome the problems, intensive research on simulation algorithms and good implementations on powerful supercomputers are necessary. In this talk we report on the optimization of a Monte Carlo simulation program forSU(3) gauge theory to run on the currently most powerful vector and vectorparallel systems. We focus on a CRAY Y-MP/C90 implementation that achieves 8.3 GFLOPS for 16 processors.