As a result of the March 28, 1979, accident at Three Mile Island Unit 2 (TMI-2), significant quantities of fission gases and volatile radionuclides, primarily radioiodine, were released into the enclosed reactor building (RB) atmosphere from the damaged reactor core. Approximately 1 yr after the accident, air samples of the RB atmosphere showed that 85Kr was the principle remaining radionuclide. The TMI-2 controlled venting experience proved that radioactive gases released during an accident causing significant core damage can be safely disposed of through atmospheric dispersion after a suitable period for radioactive decay of short-lived radioactive contaminants. The actions taken by the use of ice vests and the installation of air chillers provided a tolerable working environment within the RB for workers dressed in protective clothing. The contribution of the doses due to internally deposited radioactivity has been negligible when compared to those for radiation sources outside the body. It is clear that uptakes of radioactive material into the body have not been significant at TMI-2.