Background: Predictability has been demonstrated for the long-term success of dental implants placed simultaneously with or after a sin us-augmentation procedure. However, the time required to obtain optimal bone formation can be from 6 to 9 months or longer with grafting materials other than autogenous bone. For this reason, there is interest in a surgical technique that does not require the harvest of autogenous bone but still results in sufficient bone formation within a relatively short time frame. Methods: The purpose of this case series was to evaluate the bone formation following sinus-augmentation procedures using an allograft cellular bone matrix containing native mesenchymal stem cells. Biopsy and histologic evaluation were performed after similar to 4 months of healing. Results: Histomorphometric analysis revealed an average vital bone content of 33% (range, 22% to 40%) and an average residual graft content of 6% (range, 3% to 7%) for the five cases reported that had an average healing period of 4.1 months (range, 3 to 4.75 months). Conclusion: The high percentage of vital bone content, after a relatively short healing phase, may encourage a more rapid initiation of implant placement or restoration when a cellular grafting approach is considered. J Periodontol 2009;80:679-686.