The BRDF of a MgF2 protected Al mirror contaminated with dust particulates due to exposure to the laboratory environment has been measured and is presented for wavelengths of 633 nm, 325 nm, 121.6 nm, and 74 nm. This experimental data is compared with theoretical predictions arising from the OPALS modeling software. This model calculates the BRDF based on the measured particlate distribution found on the surface, and the optical constants of the contaminant. The OPALS software shows promise as a useful tool in the design phase of optical instruments: for drawing up contamination budgets and for incorporation into stray light analysis predicting instrument performance.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.