In order to assess the effects of hydraulic dredging on bottom sediments and on benthic populations, experimental fishing was carried out in the central part of the Venetian Lagoon. Analysis of bottom sediments showed long-term effects on sieve fractions, caused by loss of resuspended and dispersed fine particles. Infaunal samples were collected every three weeks in dredged and control areas. Immediately after dredging, significant differences in total abundance (number) and in biomass (wet weight) were observed, some persisting as long as two months. There were also long-term effects on biocenoses, related to changes in sediment particle size and the mechanical action of the dredge on marine Phanerogames (i. e. Zostera spp.). It is hypothesized that the recovery of the infaunal community, which was slow compared with recovery times recorded for this type of fishing at sea, is related to the medium/low energy conditions of the lagoon environment. It is concluded that hydraulic dredging produces considerable negative effects on the bottom environment of the Venetian Lagoon.