The National Cancer Policy Board and the Board on Science, Engineering, and Economic Policy convened a workshop in January 2004 on Economic Models of Colorectal Cancer (CRC) Screening in Average-Risk Adults . The purpose of the workshop was to explore the reasons for differences among leading cost-effectiveness analysis (CEA) models of CRC screening, which public health policy makers increasingly rely on to help them sift through the many choices confronting them. Participants discussed the results of a collaborative pre-workshop exercise undertaken by five research teams that have developed and maintained comprehensive models of CRC screening in average-risk adults, to gain insight into each model s structure and assumptions and possible explanations for differences in their published analyses. Workshop participants also examined the current state of knowledge on key inputs to the models with a view toward identifying areas where further research may be warranted. This document summarized the presentations and discussion at the workshop.