In parallel with overall population trends, the incidence of paediatric ulcerative colitis (UC) has remained stable, whereas that of paediatric Crohn's disease (CD) has increased in recent decades. Still rare among preschool children, the incidence of both UC and CD rises steadily from middle childhood through adolescence. There is an unexplained preponderance of males with early-onset CD, and an equal gender distribution in paediatric UC. Observations on the familiality of paediatric inflammatory bowel disease (IBD) suggest that genetic susceptibility is particularly important to disease pathogenesis in young patients. In comparison to adult-onset disease, childhood UC is usually extensive but the anatomic localization of paediatric CD varies, as in adults. UC manifests uniformly as bloody diarrhea whereas the symptomatology of paediatric CD is much more diverse. Linear growth impairment frequently complicates chronic intestinal inflammation in paediatric CD. Key contributing factors have been defined; better immunomodulatory therapy and emerging biologic agents will potentially reduce its prevalence.