Thermoluminescence measurements have been made as a function of pressure to 40 kbars on three ZnS phosphors, two doped with Cu+and Cl−, and one doped with Ag+and Cl−. The apparatus is briefly described. The major features of the thermoluminescent spectra were a low‐temperature peak which shifted to lower temperature with increasing pressure and a high‐temperature peak which shifted rapidly to higher temperature. The entire spectrum decreased in intensity, which is consistent with House’s measurements of the steady‐state intensity. Data from three different heating rates gave consistent values for the trap depth. The change in energy of the electron trap with pressure obtained from these thermoluminescence measurements was quantitatively consistent with House’s calculations based on steady‐state data.