The establishment of a network to assess pollutant effects is a current concern of international bodies such as the North Sea Task Force, the International Council for the Exploration of the Sea and the Intergovernmental Oceanographic Commission. With respect to the French coasts, three major considerations have been defined : the choice of monitoring areas ; the determination of a target species according to different criteria such as wide distribution, limited migration and contact with pollutant-rich sediments; and the selection of suitable parameters. This paper concerns the strategy adopted for the French coast. Ethoxyresorufin-O-deethylase, a specific cytochrome P450-dependent monooxygenase, measured by a simple microplate assay, was selected as an indicator of polyaromatic hydrocarbon and polychlorobiphenyl effects in Callionymus lyra and Limanda limanda in measurements conducted in the Seine Bay. Assessment of metallothionein in oysters in the Gironde Estuary indicated the absence of induction along a cadmium contamination gradient. Acetylcholinesterase was selected to measure the effects of organophosphorus and carbamates in Mytilus edulis along the French coasts and in Limanda limanda and Pleuronectes platessa from the Seine Bay. The results clearly demonstrate the feasibility of studying such parameters in the field and provide the scientific and technical basis for a network for the monitoring of pollutant effects along the French coasts.