Accurate behavioral measurement is essential to developing a science of leadership, yet accurate measurement has remained elusive. The use of follower reports of leader behavior creates challenges given that a large body of basic and applied research suggests that behavioral ratings reflect not only recall of actual behaviors, but also inferences based on semantic memory, which may vary among individuals. In this paper, we examine several explanations for rater effects that are associated with follower individual differences, contextual factors, and even research methods, such as the type of measure used, that may bias ratings of leader behavior. We also develop a conceptual model to illustrate these processes. Finally, we offer potential solutions to increase accuracy in follower reports of leader behavior. (C) 2014 Elsevier Inc. All rights reserved.