Oral supplements of live, beneficial intestinal micro- organisms for nutritional health and well-being are known as probiotics. Dietary probiotics colonize the intestinal tract, depending on the specific bacterium-to- host affinity. Bacteria are continually in competition for colonization space. The original bacterial colonies have an advantage over transient bacteria. Nevertheless, the composition of the intestinal microflora is dynamic and constantly changing. If harmful microorganisms proliferate, the equilibrium is disturbed, and it becomes difficult even for indigenous bacteria to maintain their necessary territory to colonize the intestine. Antibiotics tend to kill off both beneficial and harmful bacteria, and thus may also disturb the normal, healthy balance of intestinal microorganisms. Recent studies have indicated that probiotics might be useful in nutritionally supporting the body's natural response to inflammation and allergies, as well as stimulating the immune system. One strain in particular, Lactobacillus bulgaricus, has been used in Bulgaria for over a decade as an immune-enhancing supplement. Cell wall fragments such as lipopolysaccharides and peptidoglycans as well as phosphopolysaccharides from certain species of L. bulgaricus have been shown to stimulate lymphocyte mitogenesis thus enhancing mucosal and circulating immunity.