Calprotectin-Directed Humira® Maintenance Therapy (CADHUM)

Inclusion Criteria: 1. Men or women 18 years of age or older at the time of informed consent. 2. Crohn's disease confirmed by endoscopy with biopsies. 3. On maintenance Adalimumab at a dose of 40 mg SC q 2 weeks without concomitant immunosuppressive therapy. 4. Must be in clinical remission (CDAI \<150) at the baseline/randomization (Week 0) visit and biologic remission (both CRP \<0.8 and FCP \<167)at Week 0. 5. Prior medication for Crohn's disease may include one of the following and must have been stopped with wash out periods: Methotrexate, Azathioprine, 6-Mercaptopurine, Tacrolimus, Steroids. 6. Negative for TB, Hepatitis B-negative, and negative stool for Clostridium difficile. Exclusion Criteria 1. Unable to consent for themselves. 2. Are prisoners, students or employees of the investigators, or mentally incapacitated. 3. Are unwilling to complete this 48 week study, provide stool samples throughout, or unwilling to undergo multiple venipunctures. 4. Have a current infection with Clostridium difficile, clinically-significant intestinal stricture, history of allergy, or adverse reaction, to Adalimumab, history of sensitivity to latex. 5. Are currently using steroids or systemic immunomodulators (MTX, AZA, 6-MP, or Tacrolimus), or have used another biologic medication in the past 12 weeks other than Adalimumab, or have current or past use of Kineret® (Anakinra) or Tysabri® (natalizumab). 6. Have received any live bacterial or viral vaccinations ≤ 12 weeks prior to Week 0 and must not receive 12 months after study as well as BCG vaccination 7. Are known to have congestive heart failure. 8. Have a history of, or ongoing chronic or recurrent infectious disease, including but not limited to chronic renal, chest infection (i.e. bronchiectasis) or urinary tract infection (i.e. recurrent pyelonephritis) or open, draining, or infected skin wounds or ulcers. 9. Have evidence of current clinically active and important infection. 10. Have or ever had a non-tuberculous mycobacterium infection or serious opportunistic infection (i.e. cytomegalovirus, Pneumocystis carinii, aspergillosis). 11. Are known to be infected with HIV, Hepatitis B, or Hepatitis C. 12. Have severe, progressive, or uncontrolled renal, hepatic, hematological, endocrine, pulmonary, cardiac, neurologic, cerebral, or psychiatric disease, or signs and symptoms thereof. 13. Have a known history of lymphoproliferative disease including lymphoma. Have a history of certain malignancies within five years of screening.