The release of fission products from the Three Mile Island Unit 2 plant during and following the accident was low and consisted almost entirely of noble gases and an estimated 15 Ci of 131 I. Such a small iodine release is surprising considering that 52% of the core inventory of radiocesium and 40% of the radioiodine were released from the reactor core. Significant releases of fission products to the plant systems commenced at 138 min following failure of the fuel rods. The primary pathway to the environment was through the letdown/makeup purification system to the auxiliary building plant stack. The large releases (40 to 50%) of noble gases, cesium, and iodine to the reactor building were contained within the building for 1 yr until the noble gases were released under controlled conditions.