A first step towards the compilation of a critical faunistic inventory of the Belgian marine mollusks, was the publication of a preliminary nomenclatural list in 1986. This list mentioned 136 species which until then bad been recorded alive in Belgium. Yet, such records do not necessarily mean that the species involved actually belong to our fauna. Hence, the next thing to do, was to start a more profound survey of the Belgian marine malacofauna in order to determine which species form well-established populations along our coast. This is a long term study relying upon 1) recent explorations and collecting efforts, 2) revision of the collections of the K.B.I.N. and other institutions, 3) a detailed survey of the literature and 4) field data provided by several malacologists and naturalists (e.g. members of the "Strandwerkgroep"). As a result of this work, at least 11 additional species were recorded alive along our coast, viz. Littorina mariae, L. neglecta, Caecum glabrum, Retusa obtusa, Aeolidia papillosa, Musculus discors, Ensis americanus, Tellina pygmaeus, Abra nitida, Barnea parva and Thracia papyracea . For several other species, detailed information on their distribution in Belgium is now also available (e.g. for the Littorinidae). All our distributional data will be incorporated in the "5ea Area Atlas" edited by D.R. SEAWARD (the Belgian marine fauna pertains to the sea areas 513 and 553). The final purpose of this faunistic survey will be the publication of a "Fauna of the Belgian marine molluscs", in addition to a series of specialised papers on more restricted topics.