The risk for colon cancer in patients with longstanding ulcerative colitis exceeding the rectum is increased and therefore patients should be enrolled in a surveillance program eight years after the diagnosis. Until today, official international guidelines for endoscopic screening in patients with ulcerative colitis advise to take 4 biopsies every 10 centimeters (with a minimum of 32) and of each suspected visible lesion. These guidelines are merely based on consensus during expert opinion meetings rather than evidence based. Recent studies have shown that chromo-endoscopy guided biopsies significantly reduced the number of biopsies for each procedure and detected more neoplastic lesions. Chromo-endoscopy is therefore considered the gold standard in this study in which we want to compare it to the performance and efficiency of new endoscopic imaging techniques.