A series of wind-tunnel measurements was made in a simulated atmospheric boundary layer of plume characteristics in flat terrain and over a three-dimensional hill. Effluent was released at a number of elevations, upwind distances, and positions laterally offset from the centerplane defined by the wind direction and the center of the hill. Sufficient concentration measurements were made to enable the construction of plume cross sections at the downwind position of the hill center and, in a few cases, at the upwind base of the hill. These data were analyzed to provide the desired information on horizontal and vertical plume deflections and deformations over the hill.