Periodontal diseases, comprises a group of different disorders, most of which affect the supporting structures of the teeth and may ultimately result in loss of teeth. The main objective of the periodontal treatment procedures are to arrest the existing periodontal disease and thus create a healthy dentivogingival unit. It is important to restore the various components of the periodontium in their appropriate location, amounts, and relationships to each other- a process referred to as "Tissue Regeneration." This has been the aim of every periodontist and the aspiration of every patient. Guided tissue regeneration (GTR) using barrier membranes with or without bone substitute graft materials is based on the concept of epithelial exclusion in order to promote the healing of periodontal tissues in such a way that the original structure and function is preserved. This procedure aims at the reconstruction of a periodontal ligament (PDL) with well oriented and organized collagen fibers inserted in newly formed cementum and newly regenerated alveolar bone. This book provides an insight into rationale, indications and the various barrier materials used in Guided Tissue Regeneration.