Advisory committees are used often in evaluation studies, yet this practice is little discussed or reported. This issue is the first full-length text devoted to the purpose, practice, and scholarship about this type of formal, structured advice. It includes case studies and analyses of these to answer such basic topics as: * What is an evaluation advisory group (EAG)? * Why (not) use an EAG? * How to organize an EAG, and how to evaluate it? The reader will learn how to view the EAG as a structure of expertise, its use for political legitimacy, and as a response to a variety of constituencies. Guidelines on how to recruit, select, orient, train, monitor, assess, and evaluate EAG members are also included. This is the 136th volume of the Jossey-Bass quarterly report series New Directions for Evaluation, an official publication of the American Evaluation Association.