This study investigated the effect of platelet-rich fibrin (PRF) on bone regeneration of various grafting materials in rabbit calvarial defects.Two bicortical skull defects were prepared in 20 New Zealand white rabbits; 10 rabbits were treated with PRF and the other 10 were non-PRF. In both groups, autogenous bone was compare to empty defects in 5 rabbits and the composite of autogenous bone and deproteinized bovine bone versus deproteinized bovine bone (DBB) in the other five. The animals were sacrificed at 8 weeks. Bone formation was assessed by radiographic densitometry and histomorphometric analysis.The mean optical density (OD) and histomorphometric analysis (HA) of the percentage of new bone showed that the PRF groups were significantly higher than the non-PRF groups in the autogenous bone graft (OD: 0.60 ± 0.19 vs 0.36 ± 0.03; HA: 38.03 ± 4.23 vs 26.21 ± 10.58) and the empty defect (OD: 0.29 ± 0.06 vs 0.11 ± 0.06; HA: 18.81 ± 9.27 vs 6.24 ± 5.01), but not in the DBB group (OD: 1.18 ± 0.17 vs 1.07 ± 0.05; HA: 13.067 ± 3.64 vs 9.63 ± 5.47) and the composite group (OD: 0.81 ± 0.15 vs 0.91 ± 0.05; HA: 22.63 ± 3.61 vs 21.29 ± 3.52).PRF had a positive effect on bone formation when used alone or combined with autogenous bone, but not with deproteinized bovine bone.