We have described sample preparation and ion chromatography procedures that permit rapid, low-level, accurate measurement of S(IV) as SO3(2), SO4(2), and S2O6(2-) in aqueous mineral leachates. By using a pH 2.44 buffered diluent containing formaldehyde, Mn2+-catalyzed oxidation of S(IV) to SO4(2-) was prevented. These methods are applicable to a wide range of aqueous samples from the food, manufacturing, and environmental sectors, particularly when Mn2+, Fe3+, and other metal catalysts are present in the samples. The IC method for S206(2-) may be useful for environmental studies of SO2 reactivity since partial oxidation of SO2 can form SO3- radical which dimerizes to form S206(2-). It is important to remember these methods use standard commercial instrumentation, columns, and eluents.