Patients with Crohn's Disease between 18 and 75 years of age and who have active disease symptoms may be eligible for this study. Candidates are screened with a review of their medical records, a medical history and physical examination, electrocardiogram, blood and urine tests, chest x-ray and tuberculin skin test. They fill out diary cards for 7 days (measuring their symptoms on the Crohn's Disease Activity Index, or CDAI) and complete a 32-item Inflammatory Bowel Disease Questionnaire (IBDQ) that surveys how their disease affects their live and activities.