Databases and Geographical Information Systems are becoming increasingly popular tools for biogeographic analysis. The reliability of the analysis depends on the accuracy of the entered data and the ability to add changes in systematics and taxonomy. The main aim of the Southern Ocean Mollusc Database (SOMBASE) project is to set up a database linked with a GIS and user-friendly front end. This system allows for the inclusion of other taxa in the future. Currently the database consists of records for 950 shelled gastropod and 136 bivalve species and 2800 sites from the Southern Ocean.The database contains fields including: 1) Taxonomic authorship, synonyms, higher level classifications, diagnostic morphological characters, and ecological features; 2) Distributional information including substrate and depth; 3) Bibliographic information.The maps can display selected sites based on any query of any field or combination of fields in the database. An online version of the database is available with distribution maps for all taxonomic levels (www.antarctica.ac.uk/SOMBASE). SOMBASE is a contribution to the Biogeiegraphic Atlas of the Southern Ocean