In front of the suspicious diagnosis of an inflammatory bowel disease (IBD), the pathologist must have adequate and complete clinical, anamnestic, instrumental informations and, if possible, the previous histopathologic examinations. This is necessary because: the diagnosis of IBD is made with exclusion criteria, different pathologic entities may have similar macroscopic and microscopic findings and the carachteristic lesions are often present in little number. The authors consider in this paper the problem of the differential diagnosis of IBD.