Objectives: The use of polypeptide growth factors (PGFs) for periodontal regeneration has recently attracted the attention of periodontal researchers. A convenient approach to obtain autologous PGFs is the use of platelet-rich plasma (PRP). There is currently great interest concerning the use of PRP in combination with bone graft materials as a treatment modality for predictably obtaining periodontal regeneration through bioengineering. The aim of the present study was to investigate the effectiveness of a regenerative procedure based on combined PRP and bovine derived xenograft (BDX) application in the treatment of deep intrabony periodontal defects. Methods: Twelve advanced chronic periodontitis patients, seven females and five males, aged 32–59 years, were included. A total of 47 intrabony defects with an associated probing depth (PD) of >6 mm and an intrabony component of > 3 mm were selected. Defects were surgically treated with PRP/BDX. At baseline and 8 months after surgery, the following clinical and radiographical parameters were recorded: plaque and sulcus bleeding indices, PD, marginal soft tissue and relative attachment levels, probing bone and radiographical bone levels. Results: No adverse event related to the use of PRP was noted. At 8 months postoperatively, clinical and radiographical parameters were improved when compared to baseline (p<0.05). The mean changes at 8 months at the deepest sites were: PD reduction of 4.61±1.25 mm, recession of 0.78±0.34 mm, attachment gain of 3.76±0.92 mm, clinical bone gain of 3.49±0.76 mm, and radiographic bone gain of 3.83±1.17 mm, respectively. Conclusions: Treatment with a combination of PRP and BDX leads to a significantly favorable clinical and radiographical improvement in deep intrabony periodontal defects. Further randomized controlled studies are needed to clarify the role played by each component of the combined therapy.