Purpose: The purpose of the article is to examine knowledge about successful principalship and discuss the methodology that has emerged throughout the history of the International Successful School Principals Project (ISSPP) and their implications for future progress. Design/methodology/approach: Historical analysis is used as a strategy for establishing the background, the expansion and the progress of ISSPP as a long-standing international research network and to discuss the development of three research strands and methodological variations over time. The analysis provides a basis for pointing at some areas that need more attention in the future. Findings: The findings suggest multiple images of the meaning of key concepts in the project and multiple theoretical and methodological orientations. There is a need to pay more attention to methodologies to make the successful cases more comparable and also to clarify the underlying assumptions of the different approaches. Originality/value: Successful school principalship is a complex phenomenon. Therefore, future studies of successful schools and leadership would benefit from the use of knowledge that draws on sociology, cultural studies and politics.