Sigma Xi is governed by volunteer officers, a Board of Directors and an Assembly of Delegates made up of chapter representatives. A president and president-elect are elected for one-year terms at the Society's annual meeting. The Assembly of Delegates also elects members of the Board of Directors for three-year terms. Sigma Xi's Standing Committees are key groups of officers and members. In most cases committee chairs are elected by the Board of Directors for three-year terms and committee members are appointed annually by the president in consultation with the president-elect. Except for the Committees on Nominations and Audit Review (whose terms coincide with the Society's annual meeting), all committee terms run from July 1 until June 30. From time to time the Board of Directors creates ad hoc committees for special purposes.