At different stages of life, probiotics can provide health benefits to the consumer. Certain benefits, such as reduction in allergy, are typical for infants. Modulation of immune function and maintenance of the intestinal microbiota are mainly beneficial during infancy/childhood and at old age. Although it may seem that in adulthood, in the prime of one's life, probiotics have fewer benefits to offer, there are still substantial health gains possible, i.e. for lactose intolerance and irritable bowel syndrome and reduction in the risk for antibiotic-associated diarrhea and respiratory tract infections. Similar benefits, but usually with a more pronounced effect, can be observed in the elderly. With the exception of the relief of lactose intolerance symptoms, the European Food Safety Authority (EFSA) has, to date, not approved any health claims for probiotics. While this may seem a contradiction to the content of the chapter, it can be explained by a difference in interpretation of what a health benefit is. According to the regulation that EFSA has to follow, a health benefit is a reduction in a disease risk factor; here, however, we discuss the clinical endpoints.