The Baltic Sea Alien Species Database is an interactive tool, and offers several information retrieving options: Database Search, Baltic Sub-regions, and Species Directory. Information from the Database is obtained from members of the Baltic Marine Biologists Working Group on Non-Indigenous Estuarine and Marine Organisms, as well as from other researchers of invasive species biology. Published papers, grey literature, environmental reports, other internet sites and the Database Questionnaire also provide information. Objectives and goals of the Database include: to provide a qualified reference system on alien species for the Baltic Sea area, to update information on the Baltic Sea alien species, to encourage the exchange of data among different geographical regions and thereby to serve a node in the Global Information System for Invasive Species.