This book has been compiled from lecture handouts prepared for the international postgraduate course on soil quality, entitled 'Soil Pollution and Soil Protection' given jointly by the universities of Wageningen (The Netherlands), Gent and Leuven (Belgium), under the auspices of the International Training Centre (PHLO) of Wageningen Agricultural University. Of the three envrionmental compartments air, water and soil, it is soil that varies most in composition under natural conditions. The effects of chemical degradatin of soil, usually referred to as 'soil pollution', depend on interactions between soil constituents and pollutants and also on the relatively large buffering capacity of soil. It is therefore very difficult to evaluate soil quality quantitatively, yet such evaluation is a prerequisite for formulating and restore soil quality. The book therefore aims to provide basic information to aid understanding of the complex problem of soil quality and its evaluation. Its intended readers are graduates who are professionally involved in soil quality and have to deal with problems of soil protection in the context of education, research, policy making or consultancy.