[en] Results of an investigation into the sensitization of the TL material CaF₂:Dy (TLD-200) by heat treatment and the possibility of the use of the material for u.v. dosimetry, are reported. It is shown that TLD-200 treated at 900⁰C has a high intrinsic sensitivity that is constant even after using it several times as a u.v. dosimeter. It is possible to prepare dosimeters of different sensitivity simply by changing the sensitization time. Treated TLD-200 is a practical dosimeter for u.v. light in the range of the germicidal lamp emission. (U.K.)