This paper briefly summarizes existing Australian data about causes of sodicity and the distribution of sodic soils in Australia. Sources of salts and sodium include atmospheric accession, salts released by weathering processes and saline groundwaters. A traditional model of sodic soil pedogenesis is contrasted with more recent data demonstrating the role of several factors including mineralogy, EC/ESP relationships and exchangeable magnesium percentage on development and behaviour of sodic soils. Limited data about the national distribution of sodic soils are presented. There has been very little recent innovative research in Australia to increase understanding of soils affected by sodicity. A number of research needs are indicated.