Aphia is a register of marine species that the Marine Data and Information Centre of the Flanders Marine Institute (VLIZ) has built and maintains since its establishment nearly five years ago. This species register (Aphia) serves as a taxonomic backbone in the management of biological data obtained by our own efforts and those coming from various national and international projects and databases. Currently, Aphia holds 20,000 taxa, including 10,000 species names of which 2,200 are relegated to synonymy. Remaining names are those of higher hierarchical levels from the systematic classification. Besides pure taxonomy, Aphia contains about 3,000 vernacular names (mainly Dutch, English, French and German) and 4,000 notes regarding species biology, ecology, distribution, habitat, taxonomy and systematics among others. All the information is referred to its source, which can be a publication, an expert or a database. More recently, VLIZ started storing distribution records for the Southern North Sea. We now have nearly 40,000 distribution records for 400 localities. By screening literature, from recent works to those dating back to the mid nineteenth century, we intend to get a more complete overview of our current and historical biodiversity. In addition, documenting nomenclature changes, recording synonymy and storing every species record will help in correctly interpreting old and grey literature. The structure of the database corresponds to the international formats of both the European Register of Marine Species (ERMS) and the International Taxonomic Information System (ITIS). It will be possible to give taxonomic input to ITIS and ERMS. Our biogeographic system is now already linked with and provides data to the European node of the global Ocean Biogeographic Information System (EurOBIS).Maintaining our species register and storing biogeographic information is a work in progress, which falls within VLIZ’s core activities of documenting and integrating marine biodiversity data.