The Australian Soil Classification provides a framework for organising knowledge about Australian soils by allocating soils to classes via a key. Since its publication in 1996, this book has been widely adopted and formally endorsed as the official national system. It has provided a means of communication among scientists and land managers and has proven to be of particular value in land resource survey and research programs, environmental studies and education. Classification is a basic requirement of all science and needs to be periodically revised as knowledge increases. This third edition of The Australian Soil Classification includes updates from a working group of the National Committee on Soil and Terrain (NCST). The main change in this edition accommodates new knowledge and understanding of the significance, nature, distribution and refined testing for soils comprising deep sands, leading to the inclusion of a new Order, the Arenosols. The introduction of the Arenosols Order led to a review and changes to Calcarosols, Tenosols and Rudosols.The Australian Soil Classification is Volume 4 in the Australian Soil and Land Survey Handbook Series.