Autologous platelet rich plasma ( PRP) has been used as an accerlerator in bone healing in dental implantology. PRP is prepared from fresh blood using centrifugation method. PRP has about 3 times more platelet count than normal blood. E-PTFE membrane has been used in guide bone regeneration procedure in dental implantology. Objective: The purpose of the study was to compare the bone regeneration rate between using PRP and e-PTFE membrane in artificial defects in canine mandible at the different healing period. Methods: Ten experimental dogs were used in this study. Four artificial defects with 5 mm diameter and 8 mm depth were performed extraorally at each lower border of the canine mandibles. One defect was filled with PRP, one was covered with e-PTFE membrane ( Gortex), one was filled with PRP and covered with e-PTFE membrane, and last defect served as control. Every two experimental animal were sacrificed at 2 weeks, 4 weeks, 6 weeks, and 12 weeks. The specimens were obtained and fixed in 10% formalin prior to histological ground section preparation using Giemsa staining. Each section was examined under microscope and digitally photographed. The digital pictures were histomorphometrically analyzed for bone regeneration rate. Results: In every healing period, the adding of PRP did not improve the bone healing rate significantly. However, the use of membrane can improve the bone healing at the first two week of healing period significantly. Conclusion: The use of PRP did not accelerate the bone regeneartion rate in canine mandibles.