Our objective was to evaluate the potential for arid-land soil dusts to contribute significantly to the content of SO₄^2- and other ions in precipitation. Soil samples collected at 102 location throughout southwestern USA deserts were extracted with distilled water and analyzed for major ionic constituents and the stable isotope ratios (³⁴S/³²S) in soluble sulfate. Most samples were dominated by Ca²⁺, and HCO₃^-, and were undersaturated with respect to gypsum. Only a weak correlation was found between Ca²⁺ and SO₄^2- in samples from upland sites. Median 34 S of soil SO4 was +6.2% compared to +3.9% reported for precipitation. However, the median ratios for CA/SO4 (12.00) and Mg/SO4 (1.84) in soil extracts were much larger than the same ratios in precipitation, suggesting that wind erosion of undisturbed desert soils is not a major source of the SO4 in precipitation. Calcite aerosols from desert soils may act to neutralize acid rain in the western USA.