In a study by the Radiation Effects Research Foundation, Hiroshima and Nagasaki, of parathyroid tumors in autopsy cases, 18 cases of parathyroid adenoma were detected among 6, 102 cases that were autopsied between 1961-77. Two of these were giant adenomas 5 cm in diameter, complicated with hyperthyroidism. Both were atomic bomb survivors of Hiroshima. One was exposed to 55 rad at the age of 51 and died at age 71. The other was exposed to 28 rad at age 44 and died at age 71. These two cases are reported with a review of the literature on parathyroid tumors that developed following irradiation of the head and neck.