This book provides an account of Photodynamic Therapy in patients with chronic periodontitis, done by using Indocyanine green dye as a photosensitizing agent. We evaluated the efficacy of this therapy on various clinical and biochemical parameters. Clinical parameters included were as- Gingival Index, Plaque Index, Clinical Attachment Level, Periodontal Pocket Depth, and Biochemical Parameters as - Reduced Glutathione (GSH) level, Oxidized Glutathione (GSSG) level, Glutathione Redox balance (GSH:GSSG). All the parameters were compared and evaluated at different time intervals. And the final results achieved were impressive.