The Multimedia Environmental Pollutant Assessment System (MEPAS) was developed by Pacific Northwest Laboratory for the US Department of Energy Office of Environment, Safety and Health. MEPAS is used to prioritize hazardous, radioactive, and mixed-waste sites, based on their potential hazard to public health. It is applicable to a wide range of environmental management and regulatory conditions. MEPAS employs a computer-assisted, simplified, contaminant-transport and exposure model. It incorporates an interactive shell program to assist the user in problem definition, data assembly and input, and report development. This manual is an introduction to MEPAS. It provides brief instructions for installing and running the computer programs and data bases on a desk-top personal computer. Detailed instructions for data entry and evaluation are provided in the MEPAS User's Guide. 26 figs.