The course of 86 children with Crohn's disease was examined during a 10-year period between 1966 and 1976. Patients were classified according to the initial site of disease. Ileocolitis was the most (52%) and colitis the least (9%) common form of disease with diffuse small bowel or ileal disease each comprising nearly 20% of the study group. These figures show a reversal from those of a previous decade when 42% of the patients had only terminal ileal disease and 17% had ileocolitis. Children with ileocolitis had the highest number of extracolonic manifestations and operations and required steroid therapy the longest. Those with only small bowel disease (with the exception of duodenal involvement) had fewer extraintestinal symptoms and operations and showed a consistently good response to medical treatment.