The pathophysiology of inflammatory bowel disease is still incompletely understood. While the development of the immune system and the establishment of the microflora take place during infancy young patients often have a more severe and extensive disease. The differences in composition and concentration of intestinal microbiota and aberrant immune responses towards the luminal bacteria prompted the concept of an 'ecological' approach to control the disease course. Probiotics, living, non pathogenic micro organisms with a beneficial effect on the host, and prebiotics, oligosaccharides promoting the growth of the beneficial microflora, have been studied to this effect. Results have so far been disappointing for Crohn's disease but encouraging for ulcerative colitis. An overview of studies using probiotics in adults or children and a perspective on specific pediatric issues is provided in this review.