Purpose: This paper seeks to describe the Swedish compulsory school system and explore a hypothesis about the relationship between structure, culture and leadership as preconditions for successful principalship. Design/methodology/approach: On the basis of earlier research, argues that a principal's success depends on how he or she alters school structures and cultures so as to foster school improvement. A successful school is defined in Swedish law and policy documents as a school that shows high performance both in academic and social goals. Based on this definition, three schools were chosen for this study. All three had increased their academic results in the last four years. Findings: Findings from the study support the hypothesis that principals contribute to the improvement of academic and social goals of their schools by the strategic work they do to change school structure and culture. Furthermore, the principals changed their school's structures and cultures in directions that were consistent with the opinions and cultures of the school district. Being able to read and work with the culture and structure of the school district was vital for principal success. Originality/value: Provides information on the important relationship between structure, culture and leadership as preconditions for successful principalship. (Contains 2 figures, 1 table, and 2 notes.)