Volumes 3 and 4 of "Characterisation and Engineering Properties of Natural Soils" are part of a unique series on this topic. The major goal of the preceding two volumes in the series, published in 2002, was to compile knowledge on natural soils into a single, authoritative reference work. Volumes 1 and 2 of "Characterisation and Engineering Properties of Natural Soils" provided a valuable reference source for researchers and professionals. Volumes 3 and 4 report on new, emergent research into the characterisation and engineering properties of soil types other than those documented in the first two volumes. Emphasis is placed on narrowing the gap between the disciplines of soil characterisation and geostatistics, drawing together knowledge of the physical understanding of microstructures on the one hand, and the impact of statistical variations on the other. Volumes 3 and 4 of "Characterisation and Engineering Properties of Natural Soils" review laboratory testing, in-situ testing, and methods of characterising natural soil variability, illustrated by actual site data. Less well-documented soil types are highlighted and the various papers take into account location and distribution, engineering geology, composition, state and index properties, structure and engineering properties. Also treated is the quality and reliability of data with reference to methods of sampling and testing, and its relevance to engineering problems. "Characterisation and Engineering Properties of Natural Soils" will be useful to consulting engineers, geotechnical engineering academics and researchers, and civil engineers and soil scientists.