Pollution prevention requires the assessment of various multimedia environmental impacts to ensure that the alternative selected most closely represents the environmental goals and priorities of the facility. While some facility's environmental policies are easy to assess (e.g., reduce TRI emissions), others require a more sophisticated assessment methodology (e.g., select the most environmentally-friendly manufacturing process). Chemical environmental impact assessment for pollution prevention can be very effective, but can only provide a scientifically defensible decision point if the methodologies, analytical tools, and data quality are consistent with the environmental goals and priorities expressed. In many assessments completed in the past, the assessment methodologies have been overly simplistic when compared to the environmental goals projected. More sophisticated chemical impact assessment methodologies have not been used in the past for a variety of reasons, including: poor study design, poor data quality, inadequate funding, inadequate computer systems and databases, and practitioner's lack of understanding. This paper will describe a broad range of assessment methodologies, the steps involved in various evaluations, various resources available to conduct pollution prevention impact assessments, and on-going methodology development.