Full-scale experimental measurements on the thermal effects of torch fires on a large spent nuclear fuel shipping cask have been obtained. The measured temperature data in the various materials of the multilayered cask are unique, since no torch tests have been previously performed on a cask. These data were obtained during a series of four torch tests that simulate a situation in which the relief valve of a liquefied gas tank railcar has been opened and the contents are vented and ignited so that the resultant torch impinges on the cask. An existing spent fuel cask was modified, and temperature data were obtained in the various materials of the multilayered cask using stainless-steel sheathed thermocouples. Results of these tests indicated that the surface temperatures for the cask with a voided neutron shield were about twice as high as those for a cask having a neutron shield filled with water. The wood in the impact limiter effectively prevented thermal penetration, limiting the temperature rise of the inner cavity to only 13°C in test 4. The maximum temperature rise of the inner cavity surface, which occurred in test 3 with the neutron shield voided, was 80°C. These thermal data will be used to refine a transient thermal analytical model, which can then be utilized to predict the thermal response of other nuclear material shipping system designs subjected to torch fire environments.