Aim: to study the effect of composite graft with and without simvastatin for treatment of intrabony defect in chronic periodontitis. Subjects and Methods: after obtaining the subjects' consent to participate in this study, twenty patients, clinically diagnosed with moderate to advanced chronic periodontitis. The patients were selected from the outpatient clinic of the Department of Oral Medicine, Periodontology, Oral Diagnosis and Oral Radiology, Faculty of Dental Medicine, Boys, Cairo, Al Azhar University. To be included in the study, patients had to have interproximal 2-wall or 3-wall intrabony defects of premolar or molar teeth, >3 mm in depth as measured by periapical radiograph. The patients were randomly assigned to two equal groups: Group I:  10 patients were surgically treated with composite graft.  Groups II: 10 patients were surgically treated with composite graft mixed with simvastatin. Patients were given oral hygiene instructions. Scaling and root planing (SRP) were performed under local anesthesia. Four weeks after SRP, every patient was reexamined and baseline data were recorded including the site-specific gingival index, plaque index^, and probing depth^. The depth of the osseous defects from radiograph was also recorded. In group I, the defects were filled with composite graft. In group II, the defects were filled with composite graft mixed with simvastatin.  Finally, the mucoperiosteal flaps were repositioned and secured in place using 3-0 silk suture. Fourteen days after surgery, sutures were removed and normal oral hygiene procedures were allowed. Clinical and radiographic parameters were evaluated at baseline and at 1, 3, and 6 months after treatment. Results: comparison between the two studied groups revealedgreater reduction in gingival index after 3 months with statistically significant difference (p ≤ 0.05). There was  greater reduction in plaque index after 3 months with statistically significant difference (p ≤ 0.05). There was non- significant reduction in pocket depth in group I and II after 1, 3 and 6 months (p<0.05). There was greater reduction in CAL in group I and II after 3 months which was found to be statistically insignificant (p<0.05). Conclusion: It can be concluded that simvastatin mixed with composite graft in patients with periodontal infrabony defects result in a greater decrease in PD and clinical attachment level gain. Simvastatin also enhances the reconstructive action of composite graft when the two materials are combined with each other for the treatment of periodontal infrabony defects as evidenced clinically and radiographically.