This issue of New Directions for Evaluation addresses the topic of evaluation policy, especially how it is informed by and affects evaluation practice. An evaluation policy is any rule or principle that a group or organization uses to guide its decisions and actions when doing evaluation. Every group and organization that engages in evaluation, including government agencies, private businesses, and nonprofit organizations, has evaluation policies. Sometimes they are formal, explicit, and written; at other times they are more implicit and ad hoc principles or norms that have simply evolved over time. Evaluation policy is a critically important issue for the field and profession of evaluation. Evaluation policies profoundly affect the day-to-day work of all evaluators. Many recent and current controversies or conflicts in the field of evaluation can be viewed, at least in part, as struggles around evaluation policy. The chapters in this issue consider evaluation policy in its many and varied settings and contexts, including extensive treatment of large-scale national evaluation policy both in the United States and in Europe. The issue brings together revised and extended versions of all of the key addresses in the presidential strand of the 2008 American Evaluation Association conference, including the presidential address, plenary speeches, and expert lectures.

This is the 123rd volume of the Jossey-Bass quarterly thematic journal New Directions for Evaluation, an official publication of the American Evaluation Association. The journal publishes empirical, methodological, and theoretical works on all aspects of evaluation. Each issue is devoted to a single topic, with contributions solicited, organized, reviewed, and edited by a guest editor or editors. Issues may take any of several forms, such as a series of related chapters, a debate, or a long article followed by brief critical commentaries

William M. K. Trochim is professor of policy analysis and management at Cornell University and is the director of evaluation for the Weill Cornell Clinical and Translational Science Center, the director of evaluation for extension and outreach, and the director of the Cornell Office for Research on Evaluation.

Melvin M. Mark is professor and head of psychology at the Pennsylvania State University. He has served as president of the American Evaluation Association and as editor of the American Journal of Evaluation (now editor emeritus).

Leslie J. Cooksy, incoming president of the American Evaluation Association, is an associate professor at the University of Delaware, where she directs a graduate program in evaluation.