The basic defueling system used at Three Mile Island Unit 2 consisted of (a) a shielded work platform mounted on the reactor vessel, (b) cylindrical canisters suspended from the work platform with intravessel debris loading, (c) dry cask handling of the canisters inside containment from the vessel to the fuel transfer system, (d) wet transfer of canisters from inside containment to the spent-fuel pit, and (e) wet storage in the spent-fuel pit until processed for shipping. Requirements for removing core debris changed substantially as knowledge of actual core conditions was attained, thwarting efforts to anticipate tooling demands. Logistics, operator proficiency, and tooling reliability determined overall productivity. Poor underwater visibility dramatically reduced productivity. Operator training and tool testing on full-scale mock-ups were essential to effective operations. The experience gained in designing and using the various tools is summarized as lessons learned.