The characterization of topsoils has recently received enhanced attention, particulary for environmental monitoring. Traditional national and international soil taxonomic classification systems hardly consider the topsoil in spite of its importance for soil quality. Consequently, the Topsoil Characterization for Sustainable Land Management (draft) (FAO 1998) was developed to be used additionally for describing topsoils and to joint it with the World Reference Base for Soil Resources (WRB) (FAO-ISRIC-ISSS 1998). Objective of the project was to prepare a revision and expansion of the Draft WRB Topsoil Characterization: - to incorporate a humus typology scheme, - to identify qualifiers, - to incorporate soil biodiversity concerns, - to test the methodology on a number of selected reference sites and theoretical examples covering a variety of ecosystems and - to initiate a network of experts. Conclusions from the project were: - In principle, a great coincidence between characterizations of humus types and topsoils was found which appears to be an appropriate basis for further correlation and, finally, incorporation in the World Reference Base for Soil Resources. - In case of forest sites the WRB Topsoil Characterization can be improved by incorporation of humus typology using qualifiers for the organic layers. - In case of grassland or arable land usually lacking organic layers topsoil characterization can be improved by using qualifiers for soil biological activity in the A horizon. - The biological qualifiers provide a good basis for soil quality assessment besides chemical and physical qualifiers. The World Reference Base of Soil Resources (WRB), the FAO topsoil characterization and an European humusform classification, which is currently under development, can be linked in the future.