The nature of the changes occuring in the high school, and the factors influencing the change process in different high schools across the nation, have been the focus of research being conducted by the Research and Improvement Process (RIP) Program of the Research and Development Center for Teacher Education. The study is designed to describe the types of changes occuring in the sample high schools, the units of change, the management of change factors, and the key situational factors influencing these efforts. This paper describes the situational factors viewed by the research staff in the High School Study. It also presents some examples of how these factors vary in their influence in different situations. Some factors were found by researchers to have more characteristic influence across cases than others; others varied more across sites. In every case, however, factors such as the nature of the change itself and its management by school leaders were found to be important to the total picture. The paper concludes with a preliminary analysis of the relation of different situational influences to the effectiveness of change efforts. (BW)