Following an application from Valio Ltd., submitted pursuant to Article 13(5) of Regulation (EC) No 1924/2006 via the Competent Authority of Finland, the Panel on Dietetic Products, Nutrition and Allergies was asked to deliver an opinion on the scientific substantiation of a health claim related to Lactobacillus rhamnosus GG (LGG) and maintenance of defence against pathogenic gastrointestinal (GI) microorganisms. LGG is sufficiently characterised. The Panel considers that the health claim refers to the defence against GI pathogens in the general population without GI infections and does not include the treatment of GI infections. Maintenance of defence against pathogenic GI microorganisms is a beneficial physiological effect. Only one out of five human intervention studies showed an effect of LGG consumption on the development of GI infections, two human intervention studies did not show an effect of LGG consumption on the stimulation of protective immune responses after oral (viral) vaccination and, in the absence of evidence for an effect of LGG consumption on the development of GI infections in the general population, studies on the treatment of GI infections, on diarrhoea during antibiotic use, or mechanistic studies, cannot be used as a source of data for the scientific substantiation of the health claim. The Panel concludes that a cause and effect relationship has not been established between the consumption of LGG and maintenance of defence against pathogenic gastrointestinal microorganisms. © European Food Safety Authority, 2011