The power excursion that occurred on April 26, 1986 at the 4th unit of the Chernobyl Nuclear Power Plant in Ukraine of the former USSR led to the worst accident in the history of nuclear energy utilization. The basic sequence of the accident was described in this report as well as the process of radioactivity release in the environment. As a result of the radioactive contamination, the area where people had to relocate amounted to about 10,000 km2. About 400,000 people were forced to leave their homes. Because of radioiodine intake by children during the early stage after the accident, about 4,000 cases of thyroid cancer were observed up to 2002. The estimate of total cancer deaths due to the Chernobyl accident ranged from 4,000 to 90,000 cases, depending on the models used by the estimators. The size of economic loss was estimated to be 235 and 180 billion US dollars for Belarus and Ukraine, respectively, for the period of 1986 – 2015. Through the investigation of the consequences of the accident, we became confident that the real scale of the Chernobyl accident can not be measured by the amount of radioactivity or radiation.