The purpose of this study is to assess the safety, effectiveness and pharmacokinetics of two levels of intravenous basiliximab in ulcerative colitis, compared to placebo.

Inclusion Criteria:

In addition to others,

• Men or women age 18-75
• Diagnosis of ulcerative colitis confirmed through screening endoscopy.
• Extent of disease must involve at least the left colon
• Moderate to severe disease (Mayo Score 6-12). Systemic features of tachycardia, fever, and/or significant anemia should not be present.
• Inadequate response despite treatment with prednisone 40 - 50 mg/day (or other oral steroid at equivalent dose) orally for a minimum of 14 days immediately preceding study entry

Exclusion Criteria:

In addition to other protocol-defined conditions,

• Pregnancy
• Stool study that shows presence of ova and parasites, significant bacterial pathogens, or C. difficile toxin
• Colitis that is indeterminate, suggestive of Crohn's disease, or isolated to the rectum, based on endoscopic and/or biopsy findings
• Severely ill patients as evidenced by protocol-defined systemic criteria
• Chest radiograph abnormalities consistent with an infectious process
• History of colonic dysplasia
• HIV infection
• Known viral Hepatitis B or C infection
• History of or exposure to tuberculosis within 6 months before study entry