SUMMARYFollowing a request from the European Commission, the Scientific Panel on Biological Hazards was asked to deliver a scientific opinion on a quantitative estimation of the impact of setting a new target for the reduction of Salmonella in breeding hens of Gallus gallus. More specifically, is asked to assess the relative impact on the prevalence of Salmonella in flocks of broilers and laying hens if a new target for reduction of Salmonella is set in breeding hens being 1% or less flocks remaining positive for all Salmonella serovars with public health significance, compared to (a) the theoretical prevalence at the end of the transitional period (1% of five serovars), and (b) the real prevalence in 2007 to be reported by the Member States. The Salmonella serovars with public health significance should be determined by the EFSA taking into account the criteria laid down in annex III to Regulation (EC) No 2160/2003. The Scientific Panel on Biological Hazards highlighted that, as previously addressed, any Salmonella serovar that is not animal host-adapted is considered capable of causing gastrointestinal illness of varying severity in humans, and thus should be considered of potential public health significance. Nevertheless, and when sufficient reliable data were available, the application of the criteria defined in the regulation that EFSA had to consider for determining the serovars with public health significance, allowed some relative categorisation of those 1 For citation purposes: Scientific Opinion of the Panel on Biological Hazards on a request from European Commission on Quantitative estimation of the impact of setting a new target for the reduction of Salmonella in breeding hens of Gallus