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Emissions of ammonia (NH3) and hydrogen sulfide (H2S) from two naturally-ventilated freestall dairy barns are presented in this paper. Barn 1 (B1) housed 400 fresh-lactating cows, while Barn 2 (B2) housed 850 non-fresh-lactating cows. The relationships between NH3 and H2S emissions and environmental factors (temperature, wind speed, and relative humidity) were evaluated. Average emissions of NH3 (32.3 g/d-cow) from the smaller B1 were approximately two times as the average emissions (16.6 g/d-cow) from the larger B2. Average emissions of H2S, however, were similar at 2.05 and 1.74 g/d-cow from B1 and B2, respectively. Average emissions of NH3 and H2S were highest in summer (July) at 44.2 and 2.78 g/d-cow from B1, and 23.2 g and 1.92 g/d-cow from B2, respectively. The lowest emissions, on the other hand, were observed in winter (January) at 27.8 and 1.92 g/d-cow from B1, and 10.2 and 0.87 g/d-cow from B2, respectively. In general, emissions of NH3 increased with temperature (R2=0.87) and wind velocity (R2=0.77), while inverse relationships were observed between NH3 emissions and relative humidity (R2=0.84). The correlations between H2S emissions and the same environmental parameters, in general, were poor (R2 = 0.01). Significant spikes of H2S emissions were observed during manure-flushing events.