Exposure to environmental sulfide has been related to formation of reactive oxygen species (ROS) in vertebrate and invertebrate tissues. The present paper compares activity levels of the oxygen radical quencher superoxide dismutase (SOD) in benthic polychaetes and bivalves of differing sulphide tolerance. Total SOD activity showed no correlation to biotope related sulphide exposure of different species. Sulfide-insensitive MnSOD is present in tissues and body fluids of some sulphide adapted species. Total SOD activity was generally higher in haemoglobin containing animals, than in species lacking respiratory pigments. The sulphide-resistant MnSOD was the dominating enzymatic form in respiratory fluids of haemoglobin containing species, whereas sulphide sensitive CuZnSOD dominated in the body tissues. Bivalves without respiratory pigments had mostly SOD deficient haemolymph. The results indicate, that release of reactive oxygen species in tissues and body fluids of invertebrates could be connected to the presence of haemoglobin, rather than to sulphide oxidation.