Purpose : Platelet rich plasma (PRP) is an autologous material with many growth factors, such as BMPs, PDGF, $TGF-{eta}_1$, $TGF-{eta}_2$, VEGF, and IGF, facilitating bone healing process. The prominent osteoconductive activity and the biodegradable nature of beta-tricalciumphosphate (${eta}-TCP$) for bone grafts in animal experiments have been reported. The purpose of this study was to evaluate the effect of PRP on the osteogenesis of ${eta}-TCP$. Materials & Methods : Two artificial calvarial bone defects were made in 32 rabbits which were divided into 2 groups. In one group of 16 rabbits, autogenous bone / ${eta}-TCP$ was grafted on each side of cranial bone defect. In the other group of 16 rabbits, mixture of ${eta}-TCP$ and PRP / PRP alone was grafted on each side of the cranial bone defect. The animals were sacrificed at 2, 4, 8, and 12 weeks after surgery. The specimens were harvested and examined histologically and immunohistochemically by the expression of BMP2/4/7, PDGF, VEGF and $TGF-{eta}_1$. Results : The mean volume of new bone formation was significantly higher at 4, 8, 12 weeks in autogenous graft than that in ${eta}-TCP$. The BMP2/4 expression was significantly higher at 4 weeks in autogenous bone graft and at 4 weeks in mixture of ${eta}-TCP$ and PRP and at 12 weeks in ${eta}-TCP$. The expression of BMP7, PDGF, VEGF and $TGF-{eta}_1$ showed no significant difference in autogenous, ${eta}-TCP$, mixture of ${eta}-TCP$ and PRP, and PRP alone during grafted bone regeneration. Conclusion : The results showed that PRP had no additional value in promoting healing process of ${eta}-TCP$ grafts.