The normal colonic microflora is intimately involved in the aetiology of inflammatory bowel diseases (IBD) such as ulcerative colitis (UC) and Crohn's disease (CD). These conditions are often refractile to conventional treatments involving the employment of anti-inflammatory and immunosuppressant drugs, and this has led to a search for alternative therapies based on the use of probiotics, prebiotics and synbiotics. The majority of investigations in this area have been done with probiotics, and while there is increasing interest in the abilities of prebiotics and synbiotics to control the symptoms of IBD, very few randomised controlled trials have been reported. Although the results have been variable, human and animal studies have demonstrated that in many circumstances, these functional foods can alter the composition of the colonic microbiota, reduce inflammatory processes in the gut mucosa, and have the potential to induce disease remission. More work is needed to understand the effects of prebiotics and synbiotics on microbial communities in the gut, and their interactions with the host's immune system.