Program implementers often use evaluation results to improve the performance of their programs, but, as described in this paper, this is not always the case. Based on a review of the literature, participation in workshops, and interviews with over 50 program implementers, evaluators, and regulators in the United States and Canada, the utilization of evaluation results is investigated by asking the following questions: (1) How are program evaluation results used by program implementers and other stakeholders? (2) How are program evaluation results communicated to program implementers and other stakeholders? (3) Are the needs of program implementers being met by program evaluation? (4) What is the role of the utility regulator in facilitating the use of program evaluation results? (5) What other mechanisms can facilitate the use of program evaluation results? While there is some consensus on the answers to these questions, the type of interest in and use of evaluation varies by functional role (e.g., evaluator versus implementer), maturity of the energy efficiency market, institutional context (e.g., evaluation and implementation conducted inside the same organization, or evaluation and implementation conducted by separate entities), and by regulatory demands and evaluation interests. (C) 2008 Elsevier Ltd. All rights reserved.