The Australian Soil Classification (ASC) suggests that, owing to a lack of data available at the time of publication, modifications may be required for those soils containing sulfidic or sulfuric materials. The soil survey since undertaken for the acid sulfate soil risk maps of coastal NSW has provided sufficient data to suggest changes to the ASC, specifically with reference to horizons overlying sulfidic and sulfuric materials, and deep sulfidic materials. During the risk map survey a database of 308 sulfidic or sulfuric profiles was produced that contains descriptions, classifications, and laboratory data. It is this database that is examined in this paper. While the ASC successfully encompasses most characteristics which are important for land use, many of the risk map profiles contained an acidic, non acid sulfate, near surface layer that is not encompassed by the ASC. Hence, it is suggested here that a Supra acidic subgroup be included in the Hydrosol and Organosol Soil Orders to signify a near surface horizon with a pH <5.5 which is not sulfuric and which does not qualify as a Melacic horizon. The inclusion of an additional class to encompass deep sulfidic materials is also suggested for Hydrosols but, due to lack of data, not for other soil orders.