Examinations of the core debris from the damaged Three Mile Island Unit 2 (TMI-2) core were an important part of the overall understanding of the accident. Results from carefully designed in-pile and out-of-pile experiments were necessary for the evaluation of the core materials. In particular, results from the Power Burst Facility severe fuel damage tests conducted at the Idaho National Engineering Laboratory and unirradiated fuel bundle tests and out-of-pile materials interaction experiments conducted at Kernforschungszentrum Karlsruhe in the Federal Republic of Germany have been used to help characterize the core materials from TMI-2. The application of the results of these experiments to the characterization of the core debris for the TMI-2 accident evaluation is described.