Abstract: Gingival tissues of rats with experimental gingivitis were studied following a pulsed neodymium yttrium-aluminum-garnet （Nd:YAG）laser irradiation. The purpose of this study was to assess the effectiveness of the Nd:YAG laser in the treatment of gingival inflammation. The resurts showed that the inflammatory infiltration and the defects of epithelial and underlying connective tissues caused by the gingivitis reduced obviously after laser irradiation as determined histologically and ultrastructurally.The study indicates that the pulsed Nd: YAG laser may be a safe and powerful methed of treatment for periodontal inflammation.