Crohn's disease and ulcerative colitis are both forms of inflammatory bowel disease (IBD), which is a mostly chronic, recurring inflammation of the large or small bowel (or both). Important differences do exist between the two diseases, however. Crohn's disease is transmural (i.e., it affects the entire thickness of the bowel wall) and can occur at any location in the gastrointestinal tract, whereas ulcerative colitis is generally limited to the mucosal lining of the large intestine (see chapter 96). The age-specific incidence rates of Crohn's disease in North America for 10-to 19-yearolds is approximately 3.5 in 100,000 and appears to be increasing in all pediatric age groups (Hofley & Piccoli, 1994). Between 20% and 40% of all Crohn's diagnoses occur during childhood and adolescence, with the average age of onset estimated to be 11.5-13.0 years (Gryboski, 1994). According to most studies, the incidence rates for boys and girls are similar (Hofley & Piccoli, 1994).Crohn's disease affects different sections of the intestinal system. The particular location of the inflammation results in corresponding physical symptoms. The majority of children with Crohn's disease have inflammation of the terminal ileum (the distal portion of the small intestine), with more than half of these patients also having inflammation in segments of the colon. Approximately 10-20% of all children with Crohn's disease are affected only in the colon, and 10-15% have diffuse small bowel disease of the proximal ileum or jejunum (the middle of the three sections of the small intestine). Fewer than 5% of patients present with gastroduodenal disease (inflammation of the stomach and duodenum; Hofley & Piccoli, 1994).The three most common symptoms of Crohn's disease are abdominal pain (95%), diarrhea (77%), and weight loss (75%; Grybosky, 1994). In addition to these symptoms, children also may present with one of three distinct patterns of symptoms that are related to the specific location of the disease. Children with inflammation of the small bowel often present with nausea, vomiting, anorexia, postprandial cramping, and symptoms of dyspepsia. Malabsorption and diarrhea are common in these cases, and these children may have an increased incidence of mineral and vitamin deficiencies, especially iron, folate, and vitamin B-12