Based on a series of recent observations, mainly performed in the first half of the eighties, a survey of the actual brackish-water malacofauna, completed with autecological data available in the literature, is presented. Two mean districts have been investigated: a) the coastal area and b) the Belgian part of the Western Scheldt downstreams of Antwerp. The following species were recorded: Hydrobia ulvae , Hydrobia ventrosa , Potamopyrgus antipodarum , Assiminea grayana , Alderia modesta , Limapontia depressa , Ovatella myosotis , Leucophytia bidentata and Cerastoderma glaucum . Tergipes tergipes , Tenellia adspersa and Eubranchus sp. are known from literature as ever been found in a Belgian brackish-water habitat. The latter species could not be rediscovered during the present investigation. A current revision of Hydrobia ventrosa from the collections of the KBIN (Brussels) resulted in the discovery of Semisalsa stagnorum , a new Hydrobiidae for the Belgian fauna. This species was collected in the second half of the 19th and the first half of this century (Oostende, Lillo, Kallo) at localities which are nowadays all disappeared. This species also has to be reconfirmed for Belgium.