This article is a review of 49 human studies on clinical benefits of probiotics, from the prevention or treatment of diarrhoea, prevention of cancer, level of serum cholesterol to the stimulation of the immune system. The studied taxa include Lactobacillus spp, Bifidobacterium spp, and Enterococcus spp. The most consistent benefit is the shortening of diarrhoea caused by rotavirus infection, whereas other health benefits have to be determined with well designed placebo-controlled studies.