Ultisols and Oxisols in Malaysia are dominated by kaolinite and sesquioxides, xuhich are characterized by high Al saturation, low ECEC and Ca and/or Mg deficiencies. These acid soil infertility factors are limiting to annual crop production on the soils. A pot experiment luas conducted to investigate the chemical changes in solid phase properties of some Malaysian Ultisols and Oxisols affected by limestone, gypsum, palm oil mill effluent and rock phosphate applications. Results obtained showed that the negative charge on the clay surface of the untreated samples increased xuith an increase in soil pH. Limestone, palm oil mill effluent and rock phosphate applications increased soil pH, resulting in an increase in €ECff The CECn in the palm oil mill effluent treatment xuas further increased by an increase in the soil solution ionic strength and by the protonation of carboxyl and/or hydroxyl groups present in the organic matter. Exchangeable Ca and Mg increased, while exchangeable Al decreased significantly after palm oil mill effluent and limestone applications. It xuas observed that exchangeable K xuas reduced by gypsum and rock phosphate applications.