This paper addresses the design and evaluation of those units of airspace (sectors) under the jurisdiction of a team of air traffic controllers. The limitations of the current Federal Aviation Administration (FAA) criterion for the creation of new sectors are discussed, and other necessary considerations are enumerated. A methodology for sector design and evaluation is described that is sensitive to these additional features. The technique relates the traffic variables, route and sector geometry, and control procedures to the decision-making time (DMT) required on the part of the air traffic control (ATC) team. The term "decision-making time" is used synonymously with "controller work load," which constitutes the required sector evaluation criterion when overall ATC facility capacity and manning efficiency are desired.