In the present work, the adsorption of sulfate and fluoride by two oxisols was studied, and during the adsorption OH- released from soils were measured and the change in surface charge carried by one of the soils after the adsorption of fluoride was examined. The results show that the adsorption of sulfate by oxisols and the release of OH- from oxisols both increased with the increase of sulfate added at a constant pH, but decreased when pH became higher gradually. The adsorption and release both decreased markedly after removal of iron oxide. The ratio of OH- to SO42- for Fe-removed soils decreased to 15-34% of the original soils. These results suggest that iron oxide was the chief carrier of hydroxyl groups capable of ligand exchange with sulfate in oxisols.Compared with sulfate, however, the amount of fluoride adsorbed, OH- released during the adsorption of fluoride and the ratio of OH- to F- were much larger. The effect of iron oxide on the adsorption of fluoride by oxisols was smaller than that on In the present work, the adsorption of sulfate and fluoride by two oxisols was studied, and during the adsorption of hydroxyls released from soils were measured and the change in surface charge carried by one of the soils after the adsorption of fluoride was examined. show that the adsorption of sulfate by oxisols and the release of OH- from oxisols both increased with increase of sulfate added at a constant pH, but decreased when pH became higher gradually. The adsorption and release both decreased markedly after removal of iron oxide. The results suggest that iron oxide was the chief carrier of hydroxyl groups capable of ligand exchange with sulfate in oxisols. Compared with sulfate, However, the amount of fluoride adsorbed, OH-released during the adsorption of fluoride and the ratio of OH- to F- were much larger. The effect of iron oxide on the adsorption of fluoride by oxisols was sma ller than that on