The U.S. Courts of Appeals, working principally through three-judge panels, constitute important final arbiters of the meaning of the federal constitution, laws, and regulations and, hence, significant policymakers within the federal system. En banc rehearing-reconsideration of the decision of a three-judge panel by the full complement of judges appointed to the circuit-is an institutional device that ensures circuit decisions are in line with the established preferences of the circuit. The use of en banc varies in frequency across circuits and within circuits over time. Drawing on legal, attitudinal, and strategic perspectives of judicial behavior, we develop and test a set of integrated expectations regarding the causes of this variation. Our analysis finds support for the operation of all three models and suggests that the influence of ideology on the use of en banc in the recent era is not unique but part of a long-standing pattern.