To help relate management ideas and knowledge to educational administration, the author reviews the major theories and findings from the last 20 years on managerial leadership and discusses their relevance for school principals. He first summarizes findings from three approaches: the traits approach, emphasizing managerial motivation and skills; the power/influence approach, examining power accumulation and exercise; and the behavior approach, focusing on managerial activities and 22 behavior categories. Situational theories of leadership, according to the author, relate the three approaches to one another and to aspects of the leadership situation. Nine situational theories are reviewed, including Fiedler's contingency model, Hersey and Blanchard's maturity and task/relationship behavior theory, House's path-goal and charismatic leadership theories, Yukl's multiple linkage model, Kerr and Jermier's substitutes-for-leadership theory, Osborn and Hunt's adaptive-reactive model, Stewart's role requirements and constraints ideas, and Vroom and Yetten's normative model of participation. The author discusses the implications of the trait, power, and behavior approaches, and of some of the situational theories (especially Kerr and Jermier's, Osborn and Hunt's, Stewart's, House's path-goal, and Yukl's), for principals themselves as well as for research on principals and principal training and selection. (RW)