Due to important economic activities along the French oastline, the introduction of noxious organisms into French coastal waters, particularly by ship ballast water, may have serious consequences. After preliminary studies of ship movements in Charente Maritime, several samplings of ballast water and sediment were made. Samples were taken in five major harbours in France, along the Atlantic, Channel and Mediterranean coastlines. The main task of this first assessment was the research for exotic and possibly noxious phytoplancton. Clostridium and Vibrio bacteria were also tested for. The results are presented and discussed, with plans for further work.