The use of thermoluminescent dosimeters (TLDs) to determine gamma-ray heating in a zero-power fast-reactor environment is considered. Generalized cavity-ionization theory is used to determine the relationship between the gamma-ray heating in the medium and the energy deposited in a TLD placed within the medium. The relationship is a function of the composition of the TLD and the surrounding medium, the size of the TLD, and the gamma-ray spectrum in the medium. Calculations are presented for several combinations of these variables. Data on the response of TLD materials to fast neutrons are reviewed. The fast-neutron-induced contribution to the thermoluminescent output relative to the gamma-ray-induced contribution is investigated. The relationship between the thermoluminescent response and the energy deposited in the dosimeter is also discussed.