Developments in soil classification have accompanied parallel progress in our understanding of the soil system. However the theories behind the classifications and the purposes for which they were created have changed over time. In this groundbreaking reference, eminent soil scientists, many of whom were involved in the design of their respective national or international systems, evaluate developments in soil classification during the last century. They review the concepts, practices, and goals that led to the creation of individual classification systems and recommend modifications to national and international classification systems to meet new demands.