This volume describes the proceedin9s of a ~IATO Advanced Study Institute on Technological Risk Assessment, held ~1ay 20-31, 1981, at Erice, Sicily. The approach taken at the Erice meetin0 was to explore the multidisciplinary nature of risk assessment, rather than to focus on any single aspect or approach to risk assessment. This approach provided an overview of many different types of risk assessment 'Iork, as well as insilJht into how these different a~proaches are combined to provide esti~ates of risk. Additionally, understanding of the perception and public reaction to risk, and market and regulatory methods that lead to risk man- agement were major topics of the meetin~. All but two of the papers in this volume were presented at that meeting by lecturers or ~artici~ants; the papers by Drs. Lave and Vesely were added by the editors because they are excellent complements to the other ra~ers. Also included is a comprehensive bibliography on the policy-related risk literature; this was developed by Covello and Abernathy of the U.S. ~4ational Science Foundation program on Technology Assess~ent and Risk Analysis.