Probiotics are defined as "live microorganisms, which, when administered in adequate amounts, confer a health benefit on the host." Most probiotics are lactic acid producing bacteria that are endogenous to the human GI (gastrointestinal) tract and are commonly utilized in the fermentation of food products, such as yogurt. Disturbances in the composition of the bacterial flora of the GI tract are associated with diarrhea and inflammatory bowel disease (IBD), and consumption of some strains of probiotic bacteria are very effective for treating diarrhea and possibly individuals with ulcerative colitis (UC). We will test the effects of 3 strains of probiotic bacteria on UC. In addition to standard medical care for UC, participants will consume a dietary supplement of 3 probiotic bacteria (Kyo-Dophilus; Lacobacillus acidophilus, Bifidobacterium bifidum, and Bifidobacterium longum) for 6 weeks. Changes in clinical symptoms and physiological markers of systemic and GI inflammation in subjects with UC will be assessed. Significant effects of the probiotics will be determined by comparing pre- and post-probiotic treatment measures for disease severity and level of inflammation and by comparing the probiotic treated group with the placebo treated control group. Any placebo effect on UC will also be assessed.