This article reviews the literature and practice concerned with the evaluation of science, technology, and innovation (STI) policies and the way these relate to theories of the innovation process. Referring to the experience of the European Union (EU), the authors review the attempts to ensure that the STI policy theory is informed by advances in the authors' understanding of the innovation process. They argue, however, that the practice of policy evaluation lags behind advances in innovation theory. Despite the efforts to promote theory-led evaluations of STI policies based on new theories of the systemic nature of innovation, evaluation practice in the EU continues to favor the development of methods implicitly based on outdated linear views of the innovation process. This article examines the reasons why this is the case and suggests that STI policy evaluation should nevertheless be supported by the evolving theoretical understanding of the innovation process. (Contains 1 diagram and 4 notes.)