Purpose: To evaluate the combination of surgical-grade calcium sulfate (SGCS) and platelet-rich plasma (PRP) for alveolar ridge preservation prior to implant placement. Materials and Methods: Five mongrel dogs were used as subjects. Four enlarged mandibular extraction sockets, 2 on each side, were created in each dog. According to a split-mouth design, the 2 anterior sockets received either SGCS/PRP (SGCS/PRPant) or were left unfilled, while the 2 posterior sockets received either SGCS/PRP (SGCS/PRPpost) or SGCS. Computerized tomographic (CT) scans were conducted at 1 day and 8 weeks postextraction to detect the change in ridge height. Bone scintigraphy was performed at 2, 4, and 6 weeks to investigate new bone formation activity. At 8 weeks, 1 dog was sacrificed for histologic and histomorphometric study. Meanwhile, implants were placed in the remaining 4 dogs. These 4 dogs were sacrificed after 3 months. Results: Less ridge resorption was observed in the anterior SGCS/PRP-filled sites compared to unfilled sites (P = .001), while no significant difference was found between the SGCS/PRPpost and SGCS groups (P = .544). Bone scintigraphy showed that sites filled with SGCS/PRP showed significantly higher count/pixel at 2 (P = .028), 4 (P = .009), and 6 weeks (P = .037) than the unfilled sites. Nevertheless, the SGCS/PRPpost group achieved significantly higher values than the SGSC group only at 2 weeks (P = .036). Histomorphometrically, the SGCS/PRPant group showed a significantly higher percentage of bone-implant contact than the unfilled group (P = .024), but no significant difference was detected between the SGCS/PRPpost and SGCS groups (P = .979). Conclusion: Grafting SGCS/PRP in fresh extraction sockets reduced alveolar ridge resorption and promoted the bone formation in this canine model. The addition of PRP to SGCS resulted in the enhancement of bone regeneration in the early phase of healing. (Pilot Clinical Trial) (More than 50 references) Keywords: alveolar ridge preservation, calcium sulfate, dental implants, platelet-rich plasma, Tc-99m-MDP