The pain-relief properties of NSAID/ASA preparations have been known for a long time. In particular, the gastrointestinal tract shows side effects such as: erosion, ulceration, and even perforation. In the upper gastrointestinal tract, our group has shown that a correct histological diagnosis of NSAID/ASA induced lesions can be made in a high percentage of cases on the basis of recognition of ischemic necrosis. NSAID/ASA induced lesions are less commonly found in the lower gastrointestinal tract. We could also demonstrate a correct histological diagnosis of NSAID-colonopathy on the basis of finding ischemic necrosis. Besides the known complications, another typical complication is diaphragm-like stenosis, which must not be mistaken for tumor stenosis. The differential diagnosis of NSAID-colonopathy includes ischemic colitis, which cannot be distinguished histologically if the exact endoscopic description is not available. Sometimes NSAID/ASA induced lesions are misdiagnosed as Crohn's disease due to the focal character of the lesions. Since all of our analyses are retrospective, the criteria developed by our group should be checked prospectively.