The ultimate goal of periodontal therapy is to regenerate the lost periodontal tissues caused by periodontitis. Several clinical procedures have been used for this purpose so far, such as bone grafts, guided tissue regeneration, or their combination. Although observations from histological studies in humans and data from controlled clinical trials have demonstrated that some of the available grafting procedures may result in periodontal regeneration in intrabony defects, complete and predictable reconstruction of periodontal tissues is still difficult to obtain. The reason is that the periodontium, once damaged, has a limited capacity for regeneration. The complex series of events associated with periodontal regeneration involves recruitment of locally derived progenitor cells to the site. The progenitor cells can subsequently differentiate into periodontal ligament-forming cells, cementoblasts, or bone-forming osteoblasts. Therefore, the key to periodontal regeneration is to stimulate the progenitor cells to re-occupy the defects. Growth factors are vital modulators during this process which can induce the migration, attachment, proliferation and differentiation of periodontal progenitor growth factor (PDGF) and transforming growth factor-β (TGF-β), have been shown to promote periodontal regeneration in vitro, in animals and in human. Alpha granules in platelets contain abundant growth factors that, when secreted, are responsible for crucial steps during tissue regeneration: increasing cell mitosis, increasing collagen production, recruiting other cells to the wound, initiating vascular in-growth, and inducing cell differentiation. Platelet-rich plasma (PRP) is an autologous concentration of platelets in plasma developed by gradient density centrifugation. It contains many growth factors, such as PDGF, TGF-β, vascular endothelial growth factor, etc. It was reported a significant enhancement of bone and soft tissue healing when PRP was used in ophthalmologic surgery, cardiac surgery, bone surgery, cosmetic surgery, and in oral and maxillofacial surgery. PRP works via the degranulation of α granules in platelets and the active secretion of growth factors, especially PDGF and TGF-β. The aim of the present study was to evaluate the clinical and radiographic results of application of PRP versus its application in conjunction with equine-derived xenograft in management of periodontal osseous defects. The present study included 15 patients (10 females, 5 males), age range (28- 45years), suffering from chronic periodontitis. They were selected, from the Outpatient Clinic of Oral Medicine and Periodontology Department, Faculty of Oral and Dental Medicine, Cairo University. Each patient presented 2 contralateral intra-bony defects, the selected sites were divided randomly (by flip a coin) into 2 treatment groups in a split mouth design. One defect was treated with open flap debridement followed by placement of PRP alone that was protected by platelet poor plasma (PPP) prior to suturing the flap. The other defect was treated with open flap debridement followed by placement of PRP in combination with equine-derived xenograft material. The clinical parameters used in the current study included probing pocket depth, clinical attachment level, gingival index, plaque index and gingival recession and recall appointments were carried out at three, six and nine months post operatively, while the radiographical parameters were evaluated presurgially and after 9 months. The results of this study revealed that both treatment modalities PRP, PRP/Graft, led to significant defect improvement, throughout the whole experimental period. And both treatment modalities compared well to each other showing no significant differences in changes in clinical and radiographic parameters.