Abstract: A cottage industry in administrative law studies the various mechanisms by which Congress, the President, and the courts exert control of administrative agencies. Restrictions on the appointment and removal of personnel, the specification of requisite procedures for agency decisionmaking, presidential prompt letters, ex ante review of proposed decisions by the Office of Management and Budget, legislative vetoes, and alterations in funding or jurisdiction all constitute potential mechanisms for the control of agency behavior. In this paper, we focus on a much more elemental mechanism of control that has surprisingly gone relatively unnoticed in the literature on administrative agencies: Congressional control of the timing of administrative action. The use of deadlines that require agency action to commence or complete by a specific date is extremely common in the modern administrative state, but even basic descriptive statistics about the frequency and nature of these mechanisms are lacking, much less a fully elaborated theory of regulatory deadlines. This paper offers the beginning of such a theory by providing a doctrinal, theoretical, and empirical analysis of deadlines in administrative law.