Leadership depends on the situation. Few social scientists would dispute the validity of this statement. But the statement can be interpreted in many different ways, depending, at least in part, on what one means by leadership. This article begins with a definition of leadership and a brief description of 3 historically important theories of leadership. The most recent of these, contingency theories, is argued to be most consistent with existing evidence and most relevant to professional practice. The Vroom, Yetton, and Jago contingency models of participation in decision making are described in depth, and their work provides the basis for identifying 3 distinct ways in which situational or contextual variables are relevant to both research on and the practice of leadership.