The presence of organic matter in soil may cause different problems depending on many factors such as type and contents of these organic materials. A testing program was carried out to study the geotechnical properties and the behavior of organic matter obtained by the addition of a sludge material brought from a sewerage treatment plant.The tests include classification, chemical, compaction, compressibility and shear strength tests. Based on the results, several conclusions have been obtained. Both liquid and plastic limits increased with increasing organic matter. Regarding compaction test, it can be noticed that both maximum dry density and optimum moisture content slightly decreased with increasing organic contents then tends to increase.Through the observation of shear strength test results, qu and cu increased with increasing organic matter contents and then tends to decrease in similar manner to the density water relation of compaction test. Regarding compressibility, organic content, water content, void ratio and arrangement of soil particles are dominant factors controlling this property. The compression behavior of organic soils varies from the compression behavior of other types of soils in two ways, first the compression of organic soils is much larger and second, the creep or secondary compression plays an important role in determining the total settlement as shown in developing a unique relationship for organic soils.