This study was designed to investigate seasonal and annual changes in the benthic macrofauna in relation to changes in hydrogen sulphide concentration in the sediment and the oxygen content in the water column. Data were collected over a three-year period from 1994 to 1997. The benthic macrofauna inhabiting the sediments of the Gulf of Gdansk, in which H₂S is permanently present, consists mostly of species with a high tolerance to oxygen deficiency and the presence of H₂S. These species are: <i>Macoma balthica</i>, <i>Harmothoe sarsi</i>, <i>Nereis diversicolor</i>, <i>Saduria entomon</i> and <i>Halicryptus spinulosus</i>, as well as <i>Pontoporeia femorata</i> and <i>Corophium volutator</i>, which are more sensitive to these factors. In 1996-1997 a decline in the abundance of almost all benthic species, and especially of the bivalve <i>M. balthica</i> at all the stations was observed in comparison to 1994-1995.