Colonoscopy is an important method for endoscopic diagnostics of colonic pathology. The ever increasing interest in colonoscopy, the growth of the number of endoscopic studies of the colon, and the development of new diagnostic endoscopic technologies for the purpose can be accounted for by the enhanced colon cancer morbidity and mortality rates. Colorectal cancer is one of the commonest forms of malignant tumours all over the world and ranks second among the causes of cancer deaths in the majority of the developed countries. Modern colonoscopy performed for diagnostics of precancerous changes and early forms of the disease implies the application of all available up-to-date technologies that allow even very small pathological structures to be identified. They include chromoscopy, narrow-band endoscopy, and the most recently proposed diagnostic technique - autofluorescence endoscopy. The most important precondition for the safety and diagnostic efficacy of colonoscopy is the adequate preparation of the intestine for the endoscopic study, intestinal sanitation during colonoscopy, the application of the most advanced methods for the passage of the colonoscope through the intestines, and detailed examination of the entire surface of the colonic mucous membrane.