In March 1976, the first in a series of intensive field studies was carried out in the Alberta Oil Sands Environmental Research Program study area in northeastern Alberta to examine the fine structure of the atmosphere and dispersion characteristics under winter conditions. The study comprised several co-ordinated sets of measurements over a two week period. These included: minisonde flights, tethersonde vertical profiles, acoustic sounder and delta-T sonde profiles, correlation spectrometer and ground level sulphur dioxide measurements, plume rise photography and background air and precipitation chemistry. Plume dispersion measurements made by aircraft were co-ordinated with the study and are reported in a separate publication. All measurements, except those for background air chemistry, were made within 20 km of Mildred Lake taking in the present oil sands processing facility of Great Canadian Oil Sands Ltd. and the future production site of Syncrude Canada Ltd. The study was successful in identifying unique features of the winter environment of the area such as diurnal formation and breakup of inversion layers, the effects of the river valley on circulation patterns, plume characteristics, pollutant deposition patterns in the snowpack and background levels of gases and particulates.