The purpose of this study is to test whether Adalimumab (at two different doses) can induce and maintain clinical remission in subjects with active Crohn's disease when compared to placebo (a substance containing no medication)

Inclusion:

• Males and females between the ages of 18 and 75 who are diagnosed with moderate to severe Crohn's Disease defined by a CDAI score of >= 220 and <= 450, normal laboratory parameters,
• are willing and able to give informed consent, and
• are able to self-inject or have a designee or healthcare professional who can inject the study medication.

Exclusion:

• History of certain types of cancer, diagnosis of ulcerative colitis,
• female or breast feeding subjects,
• surgical bowel resection(s) with in the past 6 months,
• history of listeria,
• human immunodeficiency virus (HIV),
• central nervous system demyelinating disease or untreated TB,
• history of a poorly controlled medical condition,
• unsuccessful response to infliximab or any anti-TNF agent use in the past.