The purpose of this study is to determine whether low dose Asacol® (27 mg/kg - 71 mg/kg) and high dose Asacol® (53 mg/kg - 118 mg/kg) are safe and effective when dosed as 400 mg delayed-release tablets given twice daily for 26 weeks to children and adolescents for the maintenance of remission of ulcerative colitis.

• Drug: Asacol (mesalamine), High Dose
  Patients will be randomized at baseline to high and low dose Asacol and stratified by weight. Subjects randomized to receive High Dose who weigh 17-<33 kg will receive 3 Asacol 400mg tablets in morning and 2 Asacol 400 tablets in PM. Subjects randomized to receive High Dose who weigh 33-<54 kg will receive 5 Asacol 400mg tablets in morning and 4 Asacol 400 tablets in PM. Subjects randomized to receive High Dose who weigh 54-<90 kg will receive 6 Asacol 400mg tablets in morning and 6 Asacol 400 tablets in PM.
  Other Name: Asacol; mesalamine; 5-aminosalicylic acid; 5-ASA; mesalazine
• Drug: Asacol (mesalamine), Low Dose
  Patients will be randomized at baseline to high and low dose Asacol and stratified by weight. Subjects randomized to receive Low Dose who weigh 17-<33 kg will receive 2 Asacol 400mg tablets + 1 placebo tablet in morning and 1 Asacol 400 tablet +1 placebo tablet in PM. Subjects randomized to receive Low Dose who weigh 33-<54 kg will receive 3 Asacol 400mg tablets +2 placebo tablets in morning and 2 Asacol 400 tablets + 2 placebo tablets in PM. Subjects randomized to receive Low Dose who weigh 54-<90 kg will receive 3 Asacol 400mg tablets + 3 placebo tablets in morning and 3 Asacol 400mg tablets + 3 placebo tablets in PM.
  Other Name: Asacol; mesalamine; 5-aminosalicylic acid; 5-ASA; mesalazine

• High Dose: Experimental
  Subjects who weigh 17-<33 kg will receive 2.0 g/day Asacol. Subjects who weigh 33-<54 kg will receive 3.6 g/day Asacol. Subjects who weigh 54-<90 kg will receive 4.8 g/day Asacol.
  Intervention: Drug: Asacol (mesalamine), High Dose
• Low Dose: Experimental
  Subjects who weigh 17-<33 kg will receive 1.2 g/day Asacol. Subjects who weigh 33-<54 kg will receive 2.0 g/day Asacol. Subjects who weigh 54-<90 kg will receive 2.4 g/day Asacol.
  Intervention: Drug: Asacol (mesalamine), Low Dose

Inclusion Criteria:

• male or female between the ages of 5 and 17 years, inclusive, at the time of the first dose of study medication;
• have a documented history of UC that has been successfully maintained in complete remission for at least 1 month prior to study entry
• have a baseline PUCAI score < 10
• have a body weight no less than 17 kg and no more than 90 kg
• have a history of at least 1 active episode or relapse in the last 12 months
• have taken a stable maintenance dose of oral mesalamine (or equivalent oral 5-ASA dose) for at least 1 month prior to entry in the study. Stable is defined as the same dose for the last month.
• maintained complete remission, as defined, throughout the 30-day run-in phase. Note:ONLY applies to those patients who complete the 6-week treatment in complete remission from Study 2007017 and immediately roll-over to the 30-day run-in phase
• are female patients who are pre-menarchal or have a negative urine pregnancy test and, if sexually active, practice acceptable contraception (e.g., abstinence; oral, intramuscular, or implanted hormonal contraception [at least 3 months prior to enrollment]

Exclusion Criteria:

• have a history of allergy or hypersensitivity to salicylates, aminosalicylates, or any component of the Asacol tablet
• have a significant co-existing illness or other condition(s), including but not limited to cancer or significant organic or psychiatric disease on medical history or physical examination, that, in the judgment of the Investigator, contraindicate(s) administration of the study drug and/or any study procedures
• have a history or presence of any condition causing malabsorption or an effect on gastrointestinal motility or history of extensive small bowel resection (greater than one half the length of the small intestine) causing short bowel syndrome
• any "condition" causing "malabsorption" or an effect on gastrointestinal "motility"
• have current renal disease, or a screening blood urea nitrogen (BUN) or creatinine value that is > 1.5 times the upper limit of the age appropriate normal
• have a documented history of or current hepatic disease, or liver function tests (alanine transaminase [ALT], aspartate transaminase [AST], total bilirubin) that are > 2 times the upper limit of normal
• have a history of pancreatitis
• have undergone treatment with any oral, intravenous, intramuscular, or rectally administered corticosteroids (including budesonide) within 30 days prior to the Screening visit
• have undergone treatment with any rectal mesalamine therapy within 30 days prior to the screening visit
• have undergone treatment with immunomodulatory therapy including, but not limited to: rosiglitazone, 6-mercaptopurine or azathioprine, cyclosporine, or methotrexate within 90 days prior to Screening visit
• have undergone treatment with biologic therapy including, but not limited to: infliximab,adalimumab, certolizumab or other biologic treatment of ulcerative colitis within 90 days prior to Screening visit
• have undergone treatment with antibiotics (other than topical antibiotics) including metronidazole within 7 days prior to the Screening visit
• have undergone treatment with aspirin or other nonsteroidal anti-inflammatory drugs NSAIDs) within 7 days prior to the Screening visit
• have undergone treatment with any antidiarrheals and/or antispasmodics within 30 days of the Screening visit
• have a stool examination positive for Clostridium difficile (C. difficile), bacterial pathogens, or ova and parasites. Note: Because normal gut flora may vary by geography, the Medical Monitor should be consulted before excluding a patient with a stool sample that is positive for C. difficile, bacterial pathogens or ova and parasites.