On April 28, 1986 heavy radioactive fallout from an unknown source was reported from Sweden. Later, it was discovered that two days earlier, a nuclear power reactor at Chernobyl, in the Soviet Union, had exploded releasing an enormous cloud of effluent containing 40 million Ci of 131I, 3 million Ci of 137Cs, and 50 million Ci of xenon radioisotopes. This far exceeded the 15 Ci of 131I escape in the notorious Three Mile Island accident. Chernobyl reactor IV, of an antiquated design, was a graphite-moderated reactor which suffered a steam explosion when the operating staff attempted an experiment involving preservation of safety functions during a planned shutdown. Following the explosion, a fire started in the graphite core which required ten days to control. Thirty-one persons died, two in the initial explosion and 29 of various combinations of thermal and radiation burns, and gamma irradiation. Existing emergency plans were invoked involving treatment on the scence and evacuation of seriously injured patients to a special hospital in Moscow, as well as to nearby Kiev. Later, 135,000 residents of the immediate neighborhood were surveyed and evacuated after fallout radiation levels began to rise. Fallout patterns around Europe and the northern hemisphere were closely tracked. Consequences of the accident in human and monetary terms will require years of evaluation. Although the United States has no power reactors of the Chernobyl type, the country does have a radiation disaster management plan, often rehearsed at the state level. As a consequence of Chernobyl certain international agreements dealing with radiation disaster information and management have been forged.