Ammonia (NH3) emission from a grow-finish swine (Sus scrofa) building with an underfloor manure storage pit was evaluated during warm weather during 26 June to 25 September. Average daily mean (ADM, covering all measurement days) outdoor temperature was 21.8 degrees C. Ammonia concentrations, ventilation rates, and temperatures were continuously measured or recorded and 88 days of reliable data were obtained. Air samples were taken at wall and pit exhaust fans and in the pit headspace. The NH3 concentrations were monitored on-site with a chemiluminescence NH3 analyser. Ventilation rates were calculated based on operation of five wall fans, four pit fans, and the fan static pressure. The NH3 emission rates were calculated by multiplying simultaneously measured NH3 concentrations and ventilation rates of wall and pit exhaust fans. The ADM of building NH3 concentration (mean concentration of all sampling locations) was 3.9 mg m-3. The ADM building NH3 emission (sum of the emissions from all ventilation fans) was 11.2 kg day-1, equivalent to 145 g day-1 per AU (animal unit = 500 kg animal weight). The ADM emission per AU was higher than other reported values, probably due to warmer temperatures and higher ventilation rates. The building NH3 concentrations were inversely proportional to the indoor temperatures (r=-0.66) and ventilation rates (r=-0.59) and correlated well to total pig weight (r=0.49). The building NH3 emission rates were correlated to total pig weights (r=0.52) and ventilation rates (r=0.41) and were not well correlated to indoor temperatures (r=0.12).