Unsaturated soil mechanics is now increasingly recognized as an integral part of mainstream soil mechanics, and the importance and relevance of unsaturated soil mechanics for the broad field of geotechnical engineering no longer needs to be emphasized. The two volumes making up Unsaturated soils include papers from the 4^th Asia Pacific Conference on Unsaturated Soils (Newcastle, NSW, Australia, 23-25 November 2009). Experimental Studies in Unsaturated Soils and Expansive Soils contains contributions which describe field and laboratory studies in unsaturated soils and expansive soils. The keynote and overview lectures, and the contributions on theoretical and numerical advances in the field, are published in the companion volume, Theoretical and Numerical Advances in Unsaturated Soil Mechanics. Both volumes will proof to be invaluable to academics and research students in unsaturated soil mechanics.