The aims of this study were to evaluate the effects of Photogem®-mediated photosensitization on rat palatal mucosa and the biodistribution of the photosensitizer in this tissue. A solution of Photogem® (500 or 1000 mg/l) was applied to the palatal mucosa for 30 min and the exposure time to blue LED (460 nm) was 20 min (144 J/cm(2)). At 0, 1, 3, and 7 days, palatal mucosa was photographed for macroscopic analysis. After killing, the palate was removed for microscopic analysis. Thermal mapping evaluated temperature change in the tissue during irradiation. All experimental groups revealed intact mucosa in the macroscopic analysis. Tissue alterations were observed microscopically for only four out of 80 animals subjected to PDT. Fluorescence emitted by Photogem® was identified and was limited to the epithelial layer. A temperature increase from 35 to 41°C was recorded. Photogem®- mediated PDT was not toxic to the rat palatal mucosa.