Lactic acid bacteria in foods have a long history of safe use. Members of the genera Lactococcus and Lactobacillus have a ‘generally-recognised-as-safe’ status, whilst members of the genera Streptococcus and Enterococcus and some other genera of lactic acid bacteria contain opportunistic pathogens. New species and more specific strains of probiotic bacteria are constantly being identified. Prior to incorporating new strains into products their efficacy should be carefully assessed and a case-by-case evaluation of whether they share the safety status of traditional food-grade organisms should be made. Genetically modified organisms are by definition always novel. Any safety assessment is based on the decision of the novel status, including phenotypic and genotypic characterisation. Additionally, for genetically modified organisms and their products, information is required in the following categories: effects of the genetic modification on the properties of the host organism, genetic stability of the genetically modified organism, specificity of expression of novel genetic material, transfer of genetic material from genetically modified organisms, and the ability of genetically modified microorganisms to colonise and to survive in the human gut.