The study indicates the dominance o f Al in controlling the acidity o f acid Peninsular Malaysian soils. The buffering action o f the soils is dominated by AI below pH 5.5 and by the clay minerals, mainly kaolinite, at pH above pH 5.5. The rate o f extraction o f Al from the soils depends on the concentration o f the extracting solution. Lime requirement o f the soils can be obtained by multiplying the base needed to raise the pH o f the soil to 5.5 by a factor 1.3.