Within the framework of highly pathogenic avian influenza (HPAI) surveillance in Vietnam, interviews were carried out with poultry breeders and local animal health operators in 2 communes of the Red River Delta (RRD) with a view to documenting the circulation of sanitary information concerning poultry and the economic and social incentives for disseminating or withholding information. The main results demonstrate that [1] active "informal" surveillance networks exist, [2] the alert levels vary and the measures applied by the breeders are myriad and often far-removed from the official recommendations and [3] the commune veterinarian represents an interface between the formal and informal systems.