Although the radiological conditions following the Three Mile Island Unit 2 accident were extraordinary, those that had a potential impact on personnel were largely confined to the auxiliary and fuel handling buildings. The most significant pathway was the letdown, makeup, and purification system. Dose rates in some locations in the auxiliary and fuel handling buildings were in excess of 3 mSv/s (1000 R/h) during the first few days following the accident. The dose rates decreased after 3 to 4 days and stabilized after ∼1 week. Airborne radioactivity levels were initially due to the release of noble gases, and subsequently due to resuspension of surface contamination. During the first month, the mixture of fission products in the reactor coolant changed from mostly cesium to about equal amounts of strontium and cesium. This created some very high beta radiation levels. The significant strontium levels caused the contamination control limit to be reduced to one-half of the preaccident limit.