During the Research Program promoted by Co.ri.La on “Environmental quality indicators and indices for the Venice lagoon”, a toxicity index was developed that can synthesise responses from different bioassays with a variety of aquatic organisms on various phases of exposure deriving from sediment. The toxicity index is a useful tool because it classifies sediment toxicity in five classes (absent, low, medium, high and very high), permits easy representation of the information and allows ecotoxicological responses to be integrated with chemical and ecological ones.