Given the abundance of ethical scandals in businesses, sports, governments and religious organizations, it should come as no surprise that social scientists have increasingly put ethical leadership on the forefront of their research agenda. However, the literature on ethical leadership has primarily taken a normative approach, suggesting what leaders should do. This approach does not help in explaining why leaders sometimes deviate from such moral standards. In fact, little empirical work has been conducted on the question of when or why leaders actually engage in (un)ethical behavior (a behavioral ethics approach). 
The research presented in this dissertation aims to take a first step in filling this gap in the literature by identifying and examining antecedents of several ethical leader behaviors. I aim to answer important empirical questions such as: When do leaders go beyond their self-interest? When do leaders treat their followers in a fair manner? And, do leaders consistently take action against unethical followers, or do they sometimes condone unethical follower behavior? In answering such questions, I will show that aspects of leaders themselves (motives and dispositions), aspects of their followers (motives and actions) and aspects of the environment in which leaders operate interact in determining whether leaders engage in ethical leader behaviors or not