In the last 70 years, atomic disasters have occurred several times. The nuclear power plant accident at Chernobyl in 1986 in North-Central Ukraine was a unique experience in population exposures to radiation by all ages, and ongoing studies have brought a large amount of information on effects of radiation on human organism. Concerning the deteriorating global security situation and the strong rhetoric of some of the world leaders, the knowledge on the biological effects of ionizing radiation and the preventive measures designed to decrease the detrimental effects of radiation gains a new dimension, and involves all of us. This review focuses on the long-term effects of Chernobyl catastrophe especially on the endocrine system in children and in adults, and includes a summary of preventive measures in case of an atomic disaster.