Probiotics are defined as live microorganisms that may beneficially affect the host by improving the balance of the intestinal micro flora. In spontaneous animal models of inflammatory bowel disease (IBD), the influence of the enteric flora on gut inflammatory activity has been demonstrated, as germ free animals do not develop disease. Modification of the activity of the intestinal flora using probiotics has been investigated as a way of controlling IBD. However, there is still considerable work to be done before probiotics can be considered as part of the standard treatment of IBD. Probiotic cocktails should be carefully studied and the individual bacterial constituents evaluated in clinical settings. Several studies are currently underway to assess these issues. Further study of placebo controlled trial testing therapeutic role of probiotic bacteria in human trials is warranted.