Objectives:This study aimed to investigate the effect of rifampin with autogenous bone on bone regeneration in critical-size defects in the calvaria of rats.Materials and Methods:In total, 40 rats were divided into 4 groups and a 5-mm diameter of calvarial defect was made in each rat's calvarium. Control group (C), bone defects were irrigated with sterile saline; rifampin group (R), bone defects were irrigated with rifampin. In the autogenous graft group (Ag), the autogenous graft was contaminated with saliva, and the defects were filled with an autogenous graft. In the autogenous graft + rifampin group (Ag+R), the autogenous graft was contaminated with saliva and was decontaminated with rifampin, and the defects were filled with the autogenous graft. The animals were killed at 4weeks. Bone formation was assessed by micro-computed tomography scanning and stereological analyses.Results:The mean new bone volume was the greatest in the Ag/rifampin group (1.730.17), followed by the Ag group (1.50 +/- 0.05) (statistically significant difference at P<0.05). The new bone volume was the lowest in the control group (1.05 +/- 0.09); however, no difference was observed compared with the rifampin group (1.08 +/- 0.07) (P>0.05).Conclusion:This study, despite its limitations, showed that rifampin with autogenous bone increased bone regeneration in rats with critical-size defects.