Following a request from European Commission (DG SANCO), the Panel on Biological Hazards was asked to deliver a scientific opinion on the possible effect of four antimicrobial treatment substances on the emergence of antimicrobial resistance. The scope of this opinion was to assess the possible development of antimicrobial resistance when chlorine dioxide, acidified sodium chlorite, trisodium phosphate and peroxyacids are applied for poultry carcasses decontamination. For the purpose of this opinion, the terms "acquired reduced susceptibility" to the substances used for the removal of meat surface contamination and "resistance to therapeutic antimicrobials" were used. Therefore, acquired reduced susceptibility to the four substances used for the removal of meat surface contamination as well as to other substances including therapeutic antimicrobials has been considered. Abattoir was the end-point of the present scientific opinion. The BIOHAZ Panel concluded that despite a long history of use, there are currently no published data to conclude that the application of chlorine dioxide, acidified sodium chlorite, trisodium phosphate or peroxyacids to remove microbial contamination of poultry carcasses at the proposed conditions of use will lead to the occurrence of acquired reduced susceptibility to these substances. Similarly, there are currently no published data to conclude that the application of chlorine dioxide, acidified sodium chlorite, trisodium phosphate or peroxyacids to remove microbial contamination of poultry carcasses at the proposed conditions of use will lead to resistance to therapeutic antimicrobials. Uncertainties originate from the facts that acquired reduced susceptibility to some biocides other than those in question was found followed improper use of biocides. In addition, most of the evidence on acquired reduced susceptibility to some biocides other than those in question was derived from laboratory-based experiments. The Joint AFC/BIOHAZ guidance document on the submission of data for the evaluation of the efficacy of substances for the removal of microbial surface contamination of foods of animal origin should be amended. The BIOHAZ Panel recommended that any data on the potential of occurrence for acquired reduced susceptibility to biocides and/or resistance to therapeutic antimicrobials should be included. Research on the likelihood of emergence of acquired reduced susceptibility to substances used for the removal of the microbial surface contamination of foods of animal origins and other foods and resistance to therapeutic antimicrobials should be encouraged.