The costs of colonoscopy examinations at a hospital in Sweden were calculated in ten consecutive patients with ulcerative pan-colitis. Since colonoscopy in such patients is incomplete if not followed by microscopic study of the state of the colon mucosa, the costs of both the endoscopic and histological examinations were calculated together. The costs of the material used (disposable items, recycled items and durable items) and the wages for personnel involved (endoscopists, pathologists, nurses, laboratory technicians, secretaries and clerks) were calculated for each colonoscopic and histological examination. The mean cost per complete examination was US$ 223, which is moderate despite the high personnel costs in Sweden. Since the biopsy material obtained in an endoscopic examination is of value not only for conventional histological study but also for DNA analysis, periodic colonoscopy is still to be recommended in patients with long-standing ulcerative pan-colitis until new methods of cancer detection and prevention become available.