Risk assessment is the process by which environmental professionals determine clean up levels for soil and groundwater that are safe for the intended current and future use of contaminated land. The goal of this project is to develop guidance on state-of-the-art principles and practices focusing on the risk of soil and groundwater contamination to human health. The project will include modules in four primary areas: hazard identification, dose-response assessment, exposure assessment, and risk characterization. Risk communication may also be included. This project will produce a Web-based technical and regulatory guidance document and Internet-based training course that will summarize state-of-the-art methods and how to maintain high-quality risk assessments, thereby promoting greater confidence in the conclusions reached and the amount of clean-up or remediation required.