Along the estuarine gradient of the River Dese in the northern Venetian Lagoon the sessile macrobenthos of hard substrates was studied from November 1984 to June 1986 at eight sites. Samples were collected every two months by scraping the wooden piles (bricole) marking navigable canals; temperature, salinity, calcium and magnesium, dissolved oxygen, BOD₅ and transparency were measured monthly at the surface and at 2 m depth both at high and low water. Similarity (Soerensen's coefficient) and diversity (Shannon's index) were computed using abundance indices. Macrobenthic zonation seems to be mainly influenced by the salinity gradient. The forty species collected can be divided into three groups: I) true estuarine species, confined to the upper zone, with salinity less than 20; II) euryhaline species, which show a wide range of colonization; III) marine or open lagoon species which colonize the seaward zone, with salinity > 20. Only group (I) shows marked seasonal fluctuations, caused by a variable and selective environment.