The National Air Emission Monitoring Study (NAEMS) was required by a U.S. EPA air consent agreement, in which livestock producers agreed to collect air emission data in exchange for more time to report their emissions and apply for any necessary permits. Measurement of livestock air emissions from representative livestock production facilities was a major component of the study. This paper reports the ammonia component of the air emission study undertaken at a pig breeder facility in Oklahoma. Measurement of emissions of ammonia, hydrogen sulphide, particulate matter and VOCs were undertaken at a 2750-sow breeder facility comprising two, gestation barns and a 16-room, farrowing barn. A multipoint gas sampling system delivered air streams from 12 locations on the farm to gas analysers. Measurements of barn static pressure and fan operational status were combined with individual fan characteristics acquired in-situ to calculate barn ventilation rate. Rigorous quality assurance processes were used to ensure that high quality data was obtained. This data has been made available to the U.S. Environmental Protection Agency. The average daily mean (±SD) sow-specific NH3 emission rates from B1, B2 and F9 were 9.25±1.85, 9.61±1.28 and 19.1±6.0 g d -1 hd-1, respectively.