The UV radiation levels in Mexico City´s atmosphere were characterized by using polycrystalline diamond films. The UV radiation dose was measure doze was measured through the thermoluminescent response characteristic of diamond films were obtained by exposing the film to the environment for different periods. In order to quantify the UV dose detected, the thermoluminescent glow curves were compared to others obtained by exciting the same diamond film with an UV lamp of known energy. The UV radiation detection was performed on sunny, cloudy and overcast days. A null thermoluminescent response was obtained by covering the diamond films with an UV light filter. Some details of the diamond film preparation and the corresponding characterization by using micro-Raman spectroscopy and scanning electron microscopy are described, as well.