All natural waters can be used for consumption purposes if they are treated. Disinfection is one of the stages of water treatment. Disinfection by chemical methods is based on adding such oxidants as ozone, chlorine or chlorine dioxide. Water ozonation, in spite of its numerous adventages, is rarely done due to high operating costs and other inconveniences. Chlorination is the most common and cheapest method, but its application is connected with many disadvantages. That is why it is being abandoned. Chlorine dioxide is successfully applied. It reacts in a different way with substances contained in water, and fewer compounds with organic substances are formed. The author discusses the basics of this method and its advantages.