The engineering behavior of soils, wheather formed under temperate or tropicalrnconditions, is determined by certain physical characteristics designated as engineeringrnproperties. In practice, since the determination of all the engineering properties of soils isrnexpensive, often index properties, simpler and cheaper engineering characteristics whichrnare indicative are investigated.rnResidual soil is a soil material derived from the in-situ weathering and decomposition ofrnrock, which has not been transported from its original position.rnResidual tropical soils can have characteristics that are quit distinctively different fromrnthose of transported soils, That is: the conventional concept of soil mechanics is notrnapplicable to many residual soils as it consists of aggregates or crystals of weatheredrnmineral matter that break down and become progressively finer under continuousrnmanipulation.rnWestern part of Ethiopia is characterized by such soils. As mentioned in ERA (EthiopianrnRoads Authority) design manual (ERA, 2001) Residual laterites are widely available soilrnmaterial in these areas. The index properties of such soils have not been studied in detailrnas per the test recommendations for residual tropical soils. This Thesis is conducted tornindicate the index properties of soils of Asossa Town (Capital of Beneshangul Gumuze),rnwhich is located in western Ethiopia and covered by residual soils.rnIn this thesis work, the index properties of residual tropical soil have been investigated onrnthe soil specimens taken from Asossa Town by following the test proceduresrnrecommended for residual soils.rnThe specimens were tested at different sample preparation conditions prior to conductingrnthe laboratory test and resulted in different end values. The index property investigationrnin this research includes; Specific Gravity Test, Particle Size Distribution, AtterbergrnxiiirnLimit Tests and Free Swell Tests, all tests were conducted at three different testrntemperatures (at received moisture, air-dried and oven dried at a temperature of 105ornc ).rnGenerally it was found that, sample pre-treatment and commonly used soil testrnprocedures for temperate soils when applied to Asossa soils resulted in completely alteredrntest result as compared to the actual test result values obtained by following testingrnprocedures recommended for tropical soils. It was found that there is considerablernstructural water that could be destroyed by oven drying at a temperature of 105 degreesrnand must be deducted from every moisture content determinations in Atterberg Limitrntests. Sample manipulation is also found to alter the results of the Atterberg Limit valuesrnby affecting the bond between soil structures. Therefore, the appropriate test proceduresrnfor tropical soils are strongly recommended for research and practical engineeringrnapplication where such soils are likely to exist.