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For pt.IV see ibid., vol.19, no.5, p.479 (1973). In order to obtain a new tissue-equivalent TLD, thermoluminescence of BeO doped with various impurities were investigated. BeO(Na) and BeO(Li) showed efficient thermoluminescence. Glow curves of both had simple peaks near 180 C, and the emission spectrum showed a broad band in the ultra-violet region with a peak at 330 mmu. The main characteristics of the phosphors, from the veiwpoint of dosimetry, are: (1) Energy dependency: the deviation is with +or-30% for the energy range from 7 keV to 60Co-gamma energy. (2) Linear response range: 1 mR=50 R for BeO(Na), 1 mR=500 R for BeO(Li). (3) Fading: within +or-5% for the period from 5 minutes to 7 hours after exposure, where the dosimeters are calibrated at the time just 1 hour after exposure. (4) Annealing treatment to remove residual dose is easy (450 C, 10 minutes). (5) Repeating operation: more than 100 cycles of exposure-readout operation caused neither thermal damage ( less than 600 C) nor radiation damage ( less than 106 R).