We conducted the first research in the Czech Republic to measure ventilation and ammonia (NH_3) emission rates in a naturally ventilated animal building (dairy farm) during a five-day measurement period in June, combined with a three-month (May-July) monitoring of NH_3 concentration and dry deposition at 12 locations along horizontal gradients from the daily farm up to the distance of 400 m. Passive diffusion-tube samplers were used to measure monthly NH3 concentrations. Moisture (H_2O) balance was used to determine ventilation rates of the daily farm. Continuous measurements of gas concentrations (NH_3), temperature and relative humidity inside and outside the building were performed. The air exchange rate was 4.8 h^(-1) and the emission rate was 43.2 NH_3 g cow^(-1) d^(-1) for building. The emission rate was 126% of what was obtained using emission factors from the Czech national inventory (34.2 g cow^(-1) d^(-1)). NH3 concentrations and thy deposition fluxes decreased exponentially with distance from the dairy farm. Between May and July, mean predicted thy deposition fluxes ranged from 0.28 to 0.03 mu g NH_3 m^(-2)s^(-1) at a distance of 50 and 400 m from the source, respectively. Dry NH_3 deposition over the nearest 400 m from the source accounted for 11.5% of daily emissions. The results confirm the short-range dispersion of NH_3 emitted from a point source found in other studies, but it may not be the same in other situations, since dispersion of NH_3 is dependent on the surrounding land-cover and on the number of animals in a barn.