Abstract The increasing use of UV light in industry and medicine makes it necessary to have simple practical methods for UV dosimetry. To this purpose TL detectors have desirable features, but their normal intrinsic sensitivity to UV light is too low and it must be increased by a gamma preirradiation every time they are used. The authors have shown, for the first time, that a particular heat treatment on CaF2:Dy (TLD-200) increases its intrinsic sensitivity. Only TLD-200 presents this effect and its sensitivity remains constant even after repeated uses. These characteristics make TLD-200 a practical dosimeter for UV light.