This report presents data on the macrozoobenthos of 8 permanent stations in the Oosterschelde, during 1983-89. Data on abiotic characteristics of the different stations are included.Based on the 11 biomass-dominant species, the situation in the period before the construction of the storm-surge barrier (1983-84) is described. The Cockle ( Cerastoderma edule ) was dominant in biomass, comprising 21-83 % of the total biomass per station (21-83 %), except for the high and muddy station 27. The Mudsnail ( Hydrobia ulvae dominated in density (48-99 %). Total biomass is nearly completely divided over two trophic groups: filter feeders and deposit feeders. A multivariate analysis distinguished two categories of stations, sandy and muddy ones. The former are characterised by Nephtvs hombergii and Lanice conchilega and a dominance of C. edule the latter include Mya arenaria and Scrobicularia plana and very high numbers of H. ulvae Seasonal variation is important over the whole study period and more obvious in deposit feeders than in filter feeders. No overall positive or negative trend in total biomass and biomasses of trophic groups was found. At species level however, some effects of the engineering works can be demonstrated. In 1983-84 H. ulvae was numerically dominant in 6 out of 8 stations with more than 10 % of total biomass, while in 1989 this was only true for 3 stations. Scoloplos armiger became as important in relative density as H. ulvae . This polychaete have probably benefited from the decrease of its predator, the frost-sensitive Nephtvs hombergji , a situation which has maintained after the three successive severe winters 1984-85, 1985-86 and 1986-87.Considering not only the 11 biomass-dominating species, effects of the engineering works become more clearly. Tha~ marioni, a species known trom organically enriched, muddy sediments, drastically declined at the sandy stations. Species, characteristic tor dynamic, sandy places like Spio filicornis , Bathyporeia en Urothoe poseidonis increased. This corresponds ...