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Expansive soils show high volumetric changes with changes in water content. When they imbibe water during wet season, they expand and upon evaporation thereof through dry season, they shrink. Because of this alternate swelling and shrinkage, structures founded on them are severally damaged. Potentially problematic shrink-swell soils can be found almost anywhere in the world especially in arid and semi-arid regions of the tropical and temperate climate. Due to the lack of experience pertinent to characterization and dealing with problematic shrink-swell soils in Egypt, many defects appear in some structures established in development projects. Density and severity of problems associated with the presence of shrink-swell soils differ from region to another. Many factors contribute to the problem such as: soil type, soil engineering properties, foundation type, nature of development project, and the extension of development zone...etc. In this research, extensive experimental work has been performed on sixty two (62) soil samples obtained from various sites all over Egypt. The investigation targeted to assess volumetric change and moisture diffusion characteristics as well as index properties of unsaturated clayey soils. Test results confirm that volumetric change and moisture diffusion characteristics for unsaturated soils can be reasonably related to conventional soil index properties. Based on the obtained comprehensive database of results, ten (10) equations expressing relationships among different engineering properties of unsaturated shrink-swell soils in Egypt are proposed and discussed.