A review of the economic impact of disease caused by various pathogens underlines the need for further research on molluscan pathology. In France, recent problem with Bonamia required the introduction of a strategy to limit the effect of the disease. The strategy was developed in collaboration with the authorities and the oyster farming professionals. Their own part in the definition and the settlement of measures was very important. The plan pointed out the weaknesses of the measures presently available in limiting the consequences of an epizootic. The authors recommend complementary prophylaxes which need various disciplines and illustrate the results to date. We conclude by pointing out research areas that require high priority in future work. © 1986.