Eligible pediatric patients with acute flares of ileocecal Crohn's disease will be randomized to receive either PASER®, an approved delayed-release oral formulation of 4-aminosalicylic acid, in doses of 50 milligrams per kilogram three times daily for 2 weeks followed by 50 milligrams per kilogram twice daily for 2 weeks, or an identical-appearing placebo preparation.