A 79-year-old female patient with rheumatoid arthritis treated with NSAIDs on long-term developed iron-deficiency anaemia and subsequently subacute intestinal obstruction. Barium enema showed multiple diaphragm-like strictures. At colonoscopy the lumen of the ascending colon was divided into compartments by multiple thin circumferential mucosal membranes. Right hemicolectomy was carried out. The histology of the resected specimen confirmed diaphragm disease of the large bowel. Diagnosis is usually difficult, even at laparotomy, due to the poor external presence of the disease. Such lesions are rare (about 10 cases have been reported in the world literature) and are similar to those previously described in the small bowel. With the increasing world-wide use of NSAIDs, clinicians must be aware of this rare gastrointestinal complication, which may require emergency surgical intervention.