Reduction of ventilation is one of the strategies proposed to save energy in buildings, and large office buildings are appropriate targets for scrutiny. The ASHRAE Ventilation Standard 62-73 is very relevant to this subject, and proposals have been made to revise it toward lower ventilation levels. However, it might be desirable to look first at ventilation in buildings as they exist and see whether significant savings could be obtained simply by observing the present standard. This paper is an analysis of ventilation levels in the Norris Cotton Federal Office Building under restricted ventilation conditions, and it compares ventilation in the building with levels recommended in the ASHRAE standard.