Ammonia is known to be emitted from confined animal facilities in large amounts. Ammonia sampling was conducted upwind and at various locations downwind of a commercial free stall, 3500 head dairy in the San Joaquin Valley of California in the fall of 2003 and spring of 2004. Samples were collected at sites upwind of the dairy, downwind of lagoon, downwind of animal housing, and 380 m downwind of the dairy near the edge of a winter forage field. Multiple sample periods of 2 to 24 h were conducted with and without a winter forage crop growing in the surrounding field. An active chemical filter pack or denuder method was used to measure ammonia at heights of 0.5, 1, 2, 4, and 10 m. Ammonia fluxes were calculated using the USEPA approved ISC-STv3 dispersion model. Fluxes from the facility ranged from 120 to 396 mg/m2/h. Emissions were generally higher during daytime samples than nighttime samples.