Polyps of 1-5 mm are often detected during colonoscopy; these are only sporadically malignant. The removal, collection and pathological analysis of these polyps accounts for a significant part of the costs of a colonoscopy. The histologist's assessment is the gold standard and is endorsed in all guidelines for determination of the recommended interval for surveillance colonoscopy. If, however, it was possible to make a reliable endoscopic diagnosis of a polyp during colonoscopy the pathologist's assessment would not be needed. This strategy is known as optical diagnosis, and application would lead to cost-savings in the Netherlands. Before this strategy can be safely applied in practice minimal requirements for precision have to be met, and these are not fulfilled during use of white-light endoscopy. The development of electronic chromoendoscopy will lead to improved accuracy in endoscopic diagnosis of polyps.