Patients 18 years of age and older who have had Crohn's disease for at least 4 months may be eligible for this study. Candidates will be screened with a medical history and physical examination, electrocardiogram, chest X-ray, blood and urine tests, stool analysis and possibly a review of medical records. They will complete a Crohn's Disease Activity Index Questionnaire for 7 days. Participants will be randomly assigned to one of two treatment groups, as follows: