Both environmental and genetic factors contribute to the pathogenesis of inflammatory bowel disease (IBD). In Crohn’s disease , it is well established that dysregulation of the natural immune responses to luminal microbial or nutritional antigens plays a major role in aetiopathogenesis of the condition. Nevertheless, Prof Levine suggests that Crohn's Disease could be a ‘bacterial clearance disorder’ as microbial biofilms may also trigger an adaptive immune response. Diet and exposure to infections in childhood may confer protection, or predispose an individual to Crohn's Disease. In his presentation,Prof Levine uses data from epidemiological studies to explore the interplay between genetics and the environment. While genetics play a role in pathogenesis, it is also important to understand environmental effects as these may influence treatment, particularly in children with Crohn's Disease. Furthermore, environmental factors could also provide the basis for disease prevention.