<qa>  What is the Crohns Disease Activity Index?Patients 18 years of age and older who have had Crohns disease for at least 6 months, who are corticosteroid-dependent, and whose symptoms are controlled well enough so that their Crohns Disease Activity Index CDAI is less than 220, may be eligible for this study. Candidates will be screened with a medical history and review of medical records, physical examination, electrocardiogram, blood tests, urine pregnancy test for women of childbearing potential, and a questionnaire about how Crohns disease affects their life and activities. 