The interest and effort in evaluation capacity building (ECB) continues to grow enormously among organizations, funders, and evaluators. Yet a research synthesis of the ECB literature (Labin, Duffy, Meyers, Wandersman, & Lesesne, 2012) revealed major limitations in the science and practice of ECB. This forum on ECB, which includes two past presidents of the American Evaluation Association, takes a hard look at the progress and challenges of ECB. Laura Leviton challenges funders, organizations, and evaluators to answer key What, When, and How questions about ECB. Tina Taylor-Ritzler and Yolanda Suarez-Balcazar describe the importance of linking the science and practice of?ECB. Abe Wandersman describes research and practice on the Getting To Outcomes (GTO) results based approach to accountability; it is an example of connecting the Why, What, How, and Outcomes of ECB. In exploring the What of ECB, Susan Labin advances our thinking about measurement of ECB. In relation to the How of ECB, Hallie Preskill describes the need to move forward with the practice of ECB. Janet Clinton ends the forum on a positive empirical note, by providing evidence that stakeholder engagement in evaluation influences the outcomes of a program. The forum participants propose that improving the theory, implementation, methods, measures, and practice of ECB will have a significant impact on the field of evaluation and on society.