Abstract: Standing institutions have a continuous existence: examples include the United Nations, the British Parliament, the US presidency, the standing committees of the US Congress, and the Environmental Protection Agency. Intermittent institutions have a discontinuous existence: examples include the Roman dictatorship, the Estates-General of France, constitutional conventions, citizens' assemblies, the Electoral College, grand and petit juries, special prosecutors, various types of temporary courts and military tribunals, ad hoc congressional committees, and ad hoc panels such as the 9/11 Commission and base-closing commissions. Within the class of intermittent institutions, one may distinguish periodic from episodic institutions. The former come into being on a schedule set down in advance, while the latter come into being at unpredictable intervals. The Electoral College is a periodic institution, while the Roman dictatorship is an episodic one. This article attempts to identify the benefits and costs of intermittent institutions, both as a class and in their periodic and episodic varieties. The largest goals are to state some general conditions under which intermittent institutions prove superior or inferior to standing institutions, and to illuminate the temporal dimension of institutional design.