The classification properties and composition of lateritic soils, developed onrnTertiary basalt, granite and metamorphic rocks like gneiss and Shists in Nedjo,rnMendi and Assosa areas have been investigated. X-ray diffraction analysesrnshowed that the soil comprised minerals of Kaolinite and Smectite group such asrnKaolinite, Quartz, Dickite, Nacrite, Muscovite, Vermiculite, Geigerite,rnZektzerite, Tridymite and Gibbsite. Chemical analyses showed there was arnconcentration of sesquioxide minerals but no amorphous material present in thernsoil.rnComparison between moisture content at air-dry temperature (50oC with 30%rnrelative humidity) and that of oven drying at 105oC indicates that there is nornstructural water.rnFor the lateritic soil of Nedjo, Mendi and Assosa, unlike the oxidation of the freernsecondary clay minerals, the fact that there is no pronounced structural waterrnfound and/or amorphous clay minerals showed that, dehydration does notrnsignificantly affect the index and/or engineering properties of lateritic soils ofrnthis area.rnIn all the cases there is no significant difference observed between the Atterbergrnlimits obtained from test on a specimen mixed for 5min and that of 25min, thisrnindicates that the cementation of the clay particles is too high to berndisaggregated with in 25min further mixing and can also be related to the degreernof laterization. Analysis of specific gravity of the soils shows that, increase inrntemperature from its in situ condition to an air-dried equivalent of 50oC ovenrntemperature reduces specific gravity by an average of 4%.rnviiirnAnalyses of the grain size distribution and other physical properties indicatedrnthat the soil was not homogeneous within the laterite zone. Atterberg Limit testrnresults for the soil falls below the Casagrande A-line. There were significantrndifferences between the values of plasticity index determined for as receivedrncondition compared with air dried samples. High values for both the liquid andrnplastic limits may be due to the water retention capacity of porous microaggregationsrnin the soil. This can be correlated with the degree of laterisation,rnwhich depends on the ambient climate, topography and vegetation of the area.