Gypsum has been shown to ameliorate subsoil acidity in highly weathered soils. The effects of surface application of phosphogypsum on the chemical composition of five Georgia Ultisol subsoils were investigated in leaching columns. The experiment was designed in such a way as to characterize the leachate leaving the topsoil, the composition of which was substantially changed by the phosphogypsum treatment. Leachates from treated columns were higher in magnesium, potassium, and silicon, although the ionic strength never exceeded that of a saturated gypsum solution. Thus, the ameliorating solution entering the subsoil was different from the solution of phosphogypsum. After leaching, subsoil acidity was ameliorated as evidenced by reduced exchangeable Al and increased Ca in the subsoil. The reduction in Al was consistent with the formation of a solid phase such as alunite. Considerable quantities of Mg and K were leached from topsoils into subsoils. While the subsoil rooting environment may be improved by this treatment, the loss in topsoil fertility may temporarily negate this effect until these nutrients are replaced.