Objective. The purpose of the study was to evaluate the incidence of discontinuous inflammation of the appendiceal orifice in patients undergoing colonoscopy for diagnosis or surveillance of colonic disease. Material and methods. Consecutive and unselected patients subjected to colonoscopy over a 3-year period were included in a prospective study. Biopsies were taken within 2 cm of the orifice of the appendix, from the caecum and from predefined colonic segments. Discontinuous inflammation of the appendiceal orifice was defined as an area of macroscopic inflammatory changes distinct from a normal caecum of ascending colon. The biopsies were graded histologically for the presence and severity of inflammation by a pathologist without knowledge of the endoscopic findings. Results. A total of 271 patients were included. The final diagnoses were: ulcerative colitis (UC) (83 patients), Crohn's disease (CD) (54), indeterminate colitis (12), irritable bowel syndrome (IBS) (54), microscopic colitis (15) and other disease (53). Endoscopic discontinuous inflammation of the appendiceal orifice was found in 27% (95% CI: 17-38%) of patients with UC, 24% (95% CI: 13-39%) with CD, 40% (95% CI: 12-74%) with indeterminate colitis, 8% (95% CI: 0-36%) with microscopic colitis, 10% (95% CI: 3-24%) of patients with IBS and in 9% (95% CI: 2-21%) of other diseases (p < 0.05). A correlation was found for endoscopic and histological discrimination between normal and inflamed mucosa (p < 0.001). However, in 24% of patients, endoscopic inflammation was without histological signs of inflammation, primarily in an otherwise normal colon. Conclusions. Discontinuous inflammation of the appendiceal orifice is common in patients with IBD irrespective of clinical activity. However, patients with otherwise normal colon may also show congestion of this area without or with minimal microscopic inflammation.