To him who devotes his life to science, nothing can give more happiness than increasing the number of discoveries. But his cup of joy is full when the results of his studies immediately find practical application. There are not two sciences. There is only one science and the application of science, and these two activities are linked as the fruit is to the tree. Louis Pasteur Organization Development (OD) is the practical application of organization science. Drawing from several disciplines for its models, strategies, and techniques, OD focuses on the planned change of human systems and contributes to organization science through the knowledge gained from its study of complex change dynamics. The field follows Kurt Lewin’s two dicta, “In order to truly understand something, try changing it.” and “There is nothing as practical as a good theory.” The interplay between scientific theory development and its application makes OD an exciting and vibrant part of organization studies. Although a substantial number of important contributions have been made, the field has had its problems, some of which have plagued it from the beginning. Many of OD’s problems relate to its relative newness as an academic field; it has been in existence slightly more than three decades. Some derive from the enormous complexity that exists in the processes OD attempts to map. Consequently, OD’s theoretical base is unsettled; there are blurred conceptualizations of the OD process and inadequate understandings of its underlying change mechanisms. In add ion, significant questions about the robustness of OD research methods cast doubt on the validity of many research findings. Moreover, the tendency to emphasize action over systematic evaluation of OD’s — effects results in a less than desired data base for the field. Finally, the field has, for some, a “messianic” rather than scientific flavor because of its normative humanistic value-based roots. These factors make the field a difficult as well as challenging arena for both research and practice. The purpose of this chapter is to capture some of the vitality and complexity of OD and to present its theory, practice, and research in such a way that the reader can better comprehend the essence of the field, where it is now, and where it is headed. We begin with brief introductory comments on organizational change as a construct and a definition of Organization Development. We expand on this definition by presenting a perspective on organizational change based on Porras’ (Porras, 1986, 1987; Porras & Silvers, 199 1) organizational framework. A discussion of OD theory follows, concentrating on two types, change process theory and change implementation theory. Next, we broadly describe the vast array of intervention techniques currently popular in the field and discuss a few in depth. Then, we describe research findings on the effects of OD, and discuss what OD does and does