The question if a revolution is successful or not may be evaluated . from many standpoints: successful takeover of political superstructure, changes in the existing social and economic relations, effective interference in cultural and symbolical values of the nation or implementation of declared ideology.The Khmer Rouge revolution - one of the bloodiest in history - brought boundless sufferings in Cambodia. The Democratic Kampuchea was almost universally condemned on the international scene, but on the other hand, it gained a gloomy and sensational glory, because of colossal human, casualties, resulted from implementation of its concept of development. Statistically, it is very difficult to count the number of victims, especially that emotions are involved. The article contains an analysis of different calculations of the human casualties of the Cambodian tragedy. The author concludes that the most probable total number of victims can be estimated at 740,000. The number of two million indicated by several politicians and repeated by juornalists seems to be exaggerated.