The farming of shellfish, based on fishing and rearing in a natural environment, has developed considerably in recent years, particularly as a result of production of spat and juveniles in hatcheries and nurseries. The growing demand for trade in products, facilitated by modern means of transport, has increased the risks of disease spread. Using examples, the author analyses the risks incurred by shellfish farming methods and the risks linked to the present state of knowledge. Recommendations are made on prevention and the need for regulations, and difficulties encountered in this area are discussed. Finally, proposals are made to overcome the existing antagonism between marked demands and the need to protect shellfish farming.