The authors in this issue will provide state-of-the-art reviews on the use of probiotics in care of the gastroenterologic system. Articles are devoted to probiotics as treatment for IBD, chronic diarrhea, C. difficile colitis, functional bowel disease, allergic disorders, necrotizing enterocolitis, and obesity. Other articles examine the safety of probiotics, fecal biotherapy, and molecular assessment of intestinal microflora.