The impact of the main parameters of water quality which act on the life history of molluscs are presented. Two types of parameters are examined: the first are the physical-chemical parameters as temperature, salinity, turbidity, oxygen concentrations. They can be modified by perturbations directly related to human activities such as management of physical operations, e.g. constructions of dams, dredging for channels or for extraction of materials. Particular attention is given to inputs of nutrients with as consequences eutrophication and depletion of oxygen causing anoxie conditions. Attention will he focussed on some phytoplankton species like Gyrodinium aurelum which can cause mortalities in mollusc shellfish. The action of the main pollutants connected to anthropogenic actions are presented with some examples with heavy metals (mercury, zinc, copper...) and their synergetic action on larval molluscs. Antifouling substances and the tributyltin story is analysed. The second part of the review will concern the quality criteria necessary to maintain safety conditions for human consumption of products generally eaten raw. The bacteriological quality is presented as the pollutants contamination. The problems of toxic phytoplankton producing Diarrhetic Shellfish Poisoning (DSP) or Paralytic Shellfish Poisoning (PSP) in humans are analysed. As an example of organization of the monitoring aspects of the water and mollusc quality, the French monitoring is presented with three networks: the National Observation Network of the quality of marine environment (RNO), the phytoplankton monitoring network (REPHY), and the microbiological monitoring network (REMI). Main results and tendencies of these networks will he presented as bases for the definition of an optimum European network for mollusc culture areas.