In March 1976, a sulphur deposition study was conducted by sampling snow at about 55 sites around an isolated oil sand extraction plant in north-eastern Alberta, Canada. It was concluded from sulphur budget considerations that 0.14% of the sulphur emitted by the source was deposited within a radius of 25km. An SO2 deposition velocity to snow of 0.25 ± 0.20 cm s−1 was determined by simultaneously measuring sulphur deposition and ambient concentration during a pollution episode. Deposition velocities were also obtained by dividing the measured sulphur deposition rate at each site by the average ground level concentration of sulphur dioxide, computed using the Climatological Dispersion Model A set of 40 log normally distributed deposition velocities resulted with a geometric mean of 0.3–0.4cm s−1 depending on what value of background deposition was chosen. Confidence limits for the geometric mean were 0.2–0.7 cm s−1 (68% confidence) or 0.1–1.3 cm s−1 (95% confidence).