Proceedings of a workshop organized by the Standing Panel on Impact Assessment of the CGIAR Technical Advisory Committee, from May 3-5, 2001 at FAO Headquarters in Rome. The workshop was organized to instruct the formulation of operational guidelines for future impact assessments in the CGIAR on the basis of the experiences gained to date, and reviewed the, objectives, conduct, limitations, and methods used in past assessments. Discussions underscored the different purposes impact assessment serves for CGIAR Centers, Stakeholders, and Members, its critical role in accountability, in guiding future research, priorities, and resource allocation, and in providing Members with the evidence they require to justify further investment. Annex 1 contains keynote papers presented, annex 2 Center papers, annex 3 overview papers, and annex 4 background papers presented at the workshop