The emission of hydrogen sulfide (H2S) was continuously measured from two 1,000-head growing-finishing pig buildings for 6 months during 2 partial growth cycles. Hydrogen sulfide concentration was measured with an SO2 analyser. Pit chimney ventilation rates were measured with full-size ventilation sensors. Tunnel wall fan ventilation rates were calculated with fan operation times and differential static pressure. A total of 219 days and 4,544 sampling periods of reliable data subsets were obtained. Average building H2S emission rate was 591 g/d (740 mg/d.m2). Average H2S emission per animal unit (AU=500 kg animal mass) was 6.3 g/d.AU for the 2 buildings during 193 days when each of the buildings had at least 700 pigs. The H2S emissions per AU reported in the 1970s were less than 0.25% of the value obtained in this study. Average H2S emissions per AU in the second cycle were 4.8-6.1 times as high as in the first cycle in the 2 buildings due to higher temperatures and higher building airflow rates.