This paper highlights the performance of the mist chamber/ion chromatography (MC/IC) technique for measuring atmospheric sulfur dioxide (SO2) during the Gas-Phase Sulfur Intercomparison Experiment (GASIE). The technique was found to be free of interference from CO, CO2, CH4, NOx, O3, CH3SCH3, and H2O vapor. Repeated measurements at various mixing ratios of SO2 indicated that the coefficient of variation in the MC/IC measurement is 3--5% at 300--500 parts per trillion by volume (pptv), 4--7% at 150 pptv, 10% at 50 pptv, and as great as 20% near 20 pptv. In ambient air diluted five- to tenfold with zero air, the MC/IC technique tracked the other methods over the range of 30--3500 pptv. This agreement reinforced the conclusions obtained during the other test phases of GASIE. The MC/IC method has desirable features such as simplicity, small size, and weight of required equipment, sample integration times of 10 min or less, low pptv detection capabilities, and relatively modest implementation costs. In addition, a suite of important soluble gases can be measured simultaneously including nitric, formic, and acetic acids.¿ 1997 American Geophysical Union