Participants with no prior exposure to Remicade or who have been treated with Remicade in the past, who at the time of enrollment are scheduled to receive Remicade within 30 days of the Baseline Visit. Participants who have been treated in the past with Remicade must have a Remicade-free interval of no less than 90 days from the date of the next expected infusion.

Participants who are scheduled to receive standard therapy (defined as initiation or dose-increase of corticosteroids and/or immunosuppressants) that does not include Remicade. Standard therapy participants must not have previously received Remicade for UC or any other condition.

The treating physician will determine the treatment regimen and dose of Remicade.

The nine AE categories are as follows: 1) Serious infections, including infections listed as Serious AEs, tuberculosis, invasive fungal infections, other opportunistic infections, salmonellosis; 2) Infusion-related reactions including delayed hypersensitivity and anaphylactic reactions, and change in severity of infusion-related reactions over time; 3) Fatalities, analyzed by cause; 4)Worsening or new congestive heart failure; 5) Central and peripheral demyelinating neurological disorders; 6) Hematologic conditions such as idiopathic thrombocytopenic purpura, thrombotic thrombocytopenic purpura, thrombocytopenia, pancytopenia, granulocytopenia, leucopenia, hemolytic anemia, aplastic anemia, and thromboembolic events; 7) Malignancies, especially lymphoma, colorectal cancer, and skin cancer; 8) Autoimmune disorders such as lupus and lupus-like syndromes; 9) Hepatobiliary events including autoimmune hepatitis, primary sclerosing cholangitis, and liver function test abnormalities.

Participants with no prior exposure to Remicade or who have been treated with Remicade in the past, who at the time of enrollment are scheduled to receive Remicade within 30 days of the Baseline Visit. Participants who have been treated in the past with Remicade must have a Remicade-free interval of no less than 90 days from the date of the next expected infusion.

The nine AE categories are as follows: 1) Serious infections, including infections listed as Serious AEs, tuberculosis, invasive fungal infections, other opportunistic infections, salmonellosis; 2) Infusion-related reactions including delayed hypersensitivity and anaphylactic reactions, and change in severity of infusion-related reactions over time; 3) Fatalities, analyzed by cause; 4)Worsening or new congestive heart failure; 5) Central and peripheral demyelinating neurological disorders; 6) Hematologic conditions such as idiopathic thrombocytopenic purpura, thrombotic thrombocytopenic purpura, thrombocytopenia, pancytopenia, granulocytopenia, leucopenia, hemolytic anemia, aplastic anemia, and thromboembolic events; 7) Malignancies, especially lymphoma, colorectal cancer, and skin cancer; 8) Autoimmune disorders such as lupus and lupus-like syndromes; 9) Hepatobiliary events including autoimmune hepatitis, primary sclerosing cholangitis, and liver function test abnormalities.

All enrolled participants. The Remicade and Standard Therapy Groups are the number of participants who enrolled at the start of the study (N=2239). The Switched to Remicade group are the subset of participants in the Standard Therapy Group, who switched to Remicade.

Participants with no prior exposure to Remicade or who have been treated with Remicade in the past, who at the time of enrollment are scheduled to receive Remicade within 30 days of the Baseline Visit. Participants who have been treated in the past with Remicade must have a Remicade-free interval of no less than 90 days from the date of the next expected infusion.