Abstract 1. 1. The aim of this work was to evaluate the relationships between free radical scavengers and lipid peroxidation in the common mussel Mytilus edulis. 2. 2. Mussels were exposed to compounds known for their ability to produce free radicals (carbon tetrachloride, CCl 4) and reactive oxygen species via redox cycling (menadione), and the effects on digestive gland, gills and remaining tissues were studied. 3. 3. Lipid peroxidation parameters and the status of free radical scavengers (glutathione, vitamins A, E and C) were affected more by exposure to menadione than to CCl 4. 4. 4. The observed changes in the free radical scavengers content are indicative of a role in detoxication of damaging reactive species.