One hundred and five hospitalized patients had regional enterocolitis. The natural history of disease in patients with colon involvement was compared to that of another group of patients without colon involvement. Patients with colon involvement, exclusive of ileocecal disease, were more likely to be females, more likely to present themselves at a younger age, less likely to have surgery, and more likely to have a long interval between the onset of symptoms and surgical treatment. Recurrent symptoms and distal extension of regional enterocolitis were more frequently observed in patients with colon involvement. The findings challenge the current concepts of regional enterocolitis as a single disease entity.