Abstract: Clays from two Reddish-Brown Lateritic soils from the southern Mississippi Coastal Plain were fractionated and the mineral associations and weathering transformations were examined. The clays were found to be dominated by well-chloritized expansible layer silicates, gibbsite and kaolinite, with smaller amounts of quartz, mica and anatase. The abundance of gibbsite appeared to be related to the presence of expansible layer silicates and to soil pH variations. This mineral and kaolinite were found in appreciable amounts in even the finest clay fractions. Quartz and mica decreased to insignificant amounts with soil depth and decreasing particle size whereas gibbsite content of the clays rose suggesting an interrrelationship between these minerals.