Inflammatory bowel disease (IBD) comprises two idiopathic chronic relapsing and remitting inflammatory disorders of the gastrointestinal tract: ulcerative colitis and Crohn’s disease. The swift pace of advances in knowledge, understanding and innovation in the treatment of IBD has driven the need for this new edition. Here, we continue to emphasize the disturbances of host immune and environmental interactions in the etiopathogenesis of these disorders, in particular the genetically determined disturbances of host–microbe interactions. We also highlight recent improvements in our understanding of how best to use immunomodulatory and biological drugs, alone and in combination, and include the most recent innovations in this area. In the future, increasing efforts will be made to offer personalized treatment to each patient. The selection of specifc drugs only after detailed assessment of the genotype and other features of the individual will help us to identify who will respond well and who will respond badly, and thus enable us to use therapeutic agents more appositely. We must also continue to embrace the holistic approach to management of these chronic diseases. Doctors often used to overlook problems such as anemia, mood disturbance, fatigue and osteoporosis, yet each of these is a common if not always easily reversible cause of impaired quality of life for patients with IBD. In this time of increasing specialization, high technology diagnostics, molecular therapeutics and evidence-based everything, the doctor–patient relationship will come under increasing scrutiny and change. Technology helps to clarify the objective aspects of the disease but not the subjective experience – the illness – which is unique to each patient.