European Safety Registry in Ulcerative Colitis (P04808)

Inclusion Criteria: * 18 years of age, of either sex, and of any race. * Moderate-to-severe active UC, as defined by assessment by the treating physician. * Must, within 30 days of Baseline, either: * Initiate or have a dose increase of immunosuppressive drug(s), including but not limited to systemic steroids (budesonide is considered a topical steroid), azathioprine (AZA), or methotrexate (participants in this category must be Remicade naïve) or * Initiate Remicade. Participants who have been treated in the past with Remicade, but who have discontinued for any reason and who are scheduled to receive Remicade within 30 days of the baseline visit must have a Remicade-free interval of no less than 90 days from the date of the next expected infusion * Must be willing to give written informed consent and must be able to adhere to the procedural requirements of the registry. * Must be evaluated for active and inactive (latent) tuberculosis (TB) as suggested by local guidelines or as required by the Remicade label for participants starting Remicade. Exclusion Criteria: * Female who is known to be pregnant or nursing. * Previously treated with any other (investigational) biological drug for UC( other than Remicade) prior to Baseline. * In a situation or have any condition that, in the opinion of the treating physician, may interfere with their optimal participation in the registry. * Participating in a blinded trial. In addition, participants with conditions that are contraindicated in the Remicade Summary of Product Characteristics (SPC) should not be treated with Remicade.