Inclusion Criteria:

• Male and female children between the ages of six and eighteen years of age
• Endoscopic or histologic evidence of ulcerative colitis
• Active ulcerative colitis determined by primary pediatric gastroenterologist to require anti-tumor necrosis factor-alpha antibody (infliximab) therapy
• Colitis symptom score ≥2

• Screening laboratory tests that meet the following criteria (obtained within 4 weeks of enrollment):

  1. Hemoglobin >8.0 g/dL
  2. White blood cell count >3.5 x 109/L
  3. Neutrophils >1.5 x 109/L
  4. Platelets >100 x 109/L
  5. Aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase levels within 3 times the upper limit of normal.
  6. PPD skin test with skin induration <5 mm.
  7. Signed written consent from the parent/legal guardian and assent from the child to be obtained prior to enrollment.

Exclusion Criteria:

• Female subjects who are pregnant, nursing, or planning pregnancy.
• Concomitant diagnosis or history of congestive heart failure.
• Serious infection in the 3 months prior to enrollment.
• History of prior or current active or latent tuberculosis.
• Immune deficiency syndrome, including documented human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS).
• History of systemic lupus erythematosus.
• A transplanted organ.
• Known malignancy or history of malignancy within 5 years of enrollment.
• History of demyelinating disease.
• History of substance abuse.
• History of diabetes mellitus.
• Poor tolerability of venipuncture or lack of venous access during the study period.
• A live virus vaccination within 3 months of enrollment.
• Prior history of infliximab infusion or any other therapeutic agent targeted at reducing tumor necrosis factor-alpha (TNF-alpha).
• Hypersensitivity to any murine proteins or other component of the product.
• Inability to comply with study procedures