This study was carried out to determine the ways in which drying improves and develops dredged soils which exist widely in the lowlands of Korea. Before drying there were large variations in the fundamental physico-chemical properties of dredged soils collected from different places. In the sample soils, saturated hydraulic conductivity decreased gradually with an increase in bulk density with the exception that in air-dried soils a reverse trend was observed. Also in the sample soils, the sedimentation volume and the consistency limits decreased gradually with the decrease in soil water content after the air-drying treatment. The porosity of the sample soils decreased from $0.67{sim}0.87m^3/m^3;to;0.58{sim}0.66m^3/m^3$ and the liquid-phase range decreased from $0.41{sim}0.83m^3/m^3;to;0.29{sim}0.71m^3/m^3$. The solid-phase range of sample soils increased $0.13{sim}0.33m^3/m^3;to;0.24{sim}0.37m^3/m^3$ same as above with air-drying treatment. In conclusion the air-drying treatment caused an irreversible effect on some physical properties. Accordingly, these facts indicate that the effects of air-drying treatment on these properties are considered to be resulted from irreversible changes in the structural status of the sample soils.