Evaluation Capacity Building (ECB) is now being given attention, but as yet there is only a small literature about this necessary and seemingly rare process. ECB is the often-invisible work carried out within or between organizations to sustain the evaluation unit and evaluation studies. It is the ongoing, everyday work necessary to ensure quality evaluation practice. It is the vision, the political and administrative effort and management craft which continues to make possible over time the organizational conditions in which professional evaluation work is completed and used, requested, carried out and used ad infinitum. This issue is given over to the conceptualization and illumination of the evaluation capacity building process. Four case studies written by contributors show the complexity of the ECB process and its variation in different organizational structures and environments. Included are a federal agency (The Center for Disease Control and Prevention), a nationwide voluntary health organization (The American Cancer Society), an international development agency (The World Bank), and a local school district (The Anoka-Hennepin School District [Minnesota]). The editors introduce and define ECB, compare it to evaluation practice, and draw out ECB themes from the case studies. These sections are used to suggest a practical framework for understanding the core ECB checklist, and to provide a conceptual model for theory building and the collection of ECB case studies.