The goal of this study is to test whether adalimumab can induce clinical remission in subjects with active Crohn's disease who have been initially treated with infliximab and either lost response or discontinued its use as a result of intolerance to the drug.

Inclusion Criteria:

• Males and females between the ages of 18 and 75 who are diagnosed with mild to moderate Crohn's disease (defined by a CDAI [Crohn's Disease Activity Index] score of 220 and 450)
• Normal lab parameters
• Are willing to give informed consent
• Have previously used and either were intolerant to or lost response to infliximab

Exclusion Criteria:

• History of certain types of cancer
• Diagnosis of ulcerative colitis
• Pregnant female or breast feeding subjects
• Known obstructive strictures
• Surgical bowel resection in the past 6 months
• History of listeria, human immunodeficiency virus (HIV), central nervous system demyelinating disease or untreated TB (tuberculosis)
• History of poorly controlled medical conditions
• Specific doses and durations of Crohn's medications
• Subjects that have previously used infliximab and have never clinically responded unless primary non-response was due to a treatment limiting reaction to infliximab