At the present time losses due to diseases are one of main factors limiting the aquaculture development. Unceasing increase of exchanges between different countries favours the risk of introduction and propagation of new pathogen agents. At the beginning of the 90's the European Union laid the surveillance of mollusc health inside each Member State in order to protect the safety of exchanges. Indeed few measures are available to protect molluscs from diseases. Only the prophylactic approach is possible; this approach is based on a zoosanitary surveillance of mollusc populations and/or a development of resistant populations against some diseases. Created in 1986, the French network for surveillance and monitoring of mollusc health (REPAMO) ensures the survey of shellfish health status along French coasts according to the Directives 91/67/EEC and 95/70/EC. The missions of the network are: (1) the surveillance of notifiable diseases present in France (Bonamiosis due to Bonamia ostreae and Marteiliosis due to Marteilia refringens), (2) the surveillance of health state of cultured and natural populations of molluscs, (3) the study of abnormal mortalities and (4) the control of exchanges from European country or from Third country. Therefore, the aims of REPAMO network are to prevent the introduction and spread of exotic diseases inside the different areas of French production and to study the impact of pathogens already present and to survey their evolution.