The ESR analysis was carried out aiming at studying the activity of radionuclides in the dental enamel, dentin, and mandible bone tissues of reindeer of Novaya Zemlya. Doses of absorbed ionizing radiation were assessed. It was determined that the doses obtained by reindeer during underground nuclear tests were ten times higher and the activity of 90Sr was greater than those for reindeer living after the nuclear tests were suspended. Relatively high values of doses were observed for reindeer living before the nuclear weapons were invented. This fact is accounted for by an elevated level of natural radiation in the region.