Internal evaluation involves the use of internal staff to evaluate programs or issues of direct relevance to an organization. The use of internal evaluation has been growing rapidly during the last decade. Nevertheless, there is a serious gap in knowledge about internal evaluation, especially for human service and non-governmental organizations. This paper begins by examining internal evaluation within the discourse of a "new vision" of evaluation that links evaluation closely to management and practice. The paper explores the unique characteristics of internal evaluation, its strengths and weaknesses, the process of internal evaluation, steps in developing internal evaluation capacity, strategies for effective internal evaluation, and positive and negative roles of internal evaluators. It concludes with a look at some recent developments in the evolution of internal evaluation.