The brief historical survey of the discovery of Lactic Acid Bacteria (LAB) is followed by an account of the studies of LAB, since 1965 by many researchers named probiotics or biotherapeutic agents. However, as their action also involves certain antibiotic characteristics, the term "biotherapeutic bacteria" appears to suit them best. The favorable clinical effect of many LAB on various pathologic states in humans, especially in children, has now been positively demonstrated. Clinical success achieved by particular LAB in different pathologic conditions is described, with special reference to the scientifically verified effects of LGG, which has also been used in Croatia for the manufacture of fermented dairy products since 1998.