Microorganisms are intentionally added at different stages of the food and feed chain (food or feed additive, novel food or plant protection product) and are subjected to regulation and safety assessment by the European Food Safety Authority. Safety evaluation is based on application dossiers for market authorisation to the European Commission. The qualified presumption of safety (QPS) concept was developed in 20031 to provide a harmonised generic safety pre-appraisal of the above microorganisms. Unambiguously defined biological taxonomic units (TUs) are assessed for their body of knowledge, their safety and their end use. Identified safety concerns for a certain TU can be, where reasonable in number and not universally present, reflected as 'qualifications.' Strains belonging to TUs having QPS status may benefit of a fast track evaluation. The lowest TU for which the QPS status is granted is the species level for bacteria and yeasts and the family for viruses. The QPS concept is also applicable to genetically modified microorganisms used for production purposes. Based on the current body of knowledge and/or the ambiguous taxonomic position, some TUs, such as filamentous fungi, bacteriophages, Enterococcus faecium, Escherichia coli, Streptomyces spp. and Oomycetes, are not considered liable for QPS status.