CaF₂:RE and CaSO₄:RE are important phosphors. The phosphors corresponding to RE identical to Dy and Tm find applications in thermoluminescence dosimetry using ionizing radiations. Although these phosphors have been in use for several years, the mechanism of thermoluminescence in these phosphors is not well understood. The role of RE ions in emission has been clearly indicated. Two types of model have been proposed. In model 1 it is assumed that a hole recombines with a RE²⁺ ion to convert it into RE³⁺. Model 2 proposes that the energy of electron-hole recombination is transferred to the RE ion. Experimental results on CaSO₄:Eu and CaF₂:Eu are presented which show that model 2 is closer to reality.