The French network for the surveillance and monitoring of mollusc health (REPAMO) was officially set up in 1992 to control the shellfish status along the French coasts according to the European directives 91/67/EEC and 95/70/EC. The objectives are 1) the surveillance of notifiable diseases present in France (Bonamiosis and Marteiliosis of flat oysters Ostrea edulis), 2) the surveillance of health status of cultured and wild populations of molluscs, 3) the study of abnormal mortality and 4) the control of exchanges from European and third countries. In this context, a new surveillance programme, called Active Targeted Survey, part of the REPAMO, was applied in 2004 in order to improve the monitoring of the health status of the French mollusc populations (objective 2). The objective is to provide evidence of freedom regarding notifiable exotic diseases (OIE list and directive 95/70/EC annexe D) in susceptible host species. The new strategy, designed from data collected between 1990 and 2002 on the main harvested and farming species, is an active surveillance approach targeting a new mollusc species every two years. The sampling strategy including sampling method, sampling points, frequency, is defined according to the objective, the mollusc species and the targeted pathogen. In the context of this new strategy we have chosen to start with perkinsosis in clams along the French coasts. We present the theoretical approach and the data collected in 2004-2005 for clam species (Ruditapes decussatus and R. philippinarum) regarding infection with the protozoan Perkinsus olseni. Five areas, located along the French coasts, were investigated in autumn. In 2004, data demonstrated that no clam area was disease free and that prevalence and intensity of Perkinsus infection were higher in the South of France than in the English Channel.