The primary purpose of the project is to determine what is the best schedule for restarting infliximab in patients with inflammatory bowel disease (IBD) specifically ulcerative colitis and Crohn's disease, who have undergone infliximab infusions before. The primary endpoint would be the failure rate; the need to discontinue infliximab or change treatment. A secondary aim will be to determine if infliximab drug and antibody levels can predict clinical outcomes at 1 year. Other secondary outcomes include comparing short-term and long-term steroid free remission rate, and serum and fecal inflammatory markers in response to infliximab.

Inclusion Criteria:

• Subjects 18 years or older who are willing and able to provide informed consent
• HIstory of IBD (Crohn's disease, ulcerative colitis, indeterminate colitis) by standard clinical, histological, and radiographic date.
• History of stable clinical response to prior IFX induction and regular maintenance dosing, as determine by enrolling clinician.
• Prior to drug holiday, was on stable dose of infliximab for at least 3 infusions at regular maintenance intervals
• Infliximab drug holiday for at least 12 weeks.

Exclusion Criteria:

• Inability or unwillingness to provide informed consent
• Pregnant patients
• Prior history of serious infusion reaction to IFX