Probiotics are products containing beneficial bacteria and are used to create a better mixture of bacteria in the human intestine. Crohn's Disease and Ulcerative Colitis (UC) are diseases of the intestines in which the resident bacteria play an important part. Probiotics for Crohn's and Colitis describes, in straightforward English, the scientific evidence for probiotics reducing the severity of these diseases. Prebiotics, types of soluble dietary fibre that promote the growth of beneficial bacteria, are also described. Guidance is given on selecting probiotics and reassurance is given on safety. Probiotics are a 'hot topic' among people with Crohn's and UC, and for the first time all the evidence has been gathered to help patients be fully informed on the options available.