The objective of the study was to determine the osteoconductive potential of bovine-derived porous hydroxyapatite (HA) in combination with demineralized freeze-dried bone allograft (DFDBA) as an alternative to autogenous grafting in the maxillary sinus. The study involved 5 patients treated with 2-stage sinus elevation procedures using a combination of DFDBA and Osteograf/N 300 and 700. The healing time before implant placement ranged from 6 to 13 months. At the time of reentry, a bone core was harvested from each patient and processed for histologic and histomorphometric analysis. Woven and lamellar bone formation was evident in all specimens. Mean trabecular bone volume was 27.92%. The amount of newly formed bone was positively correlated with healing time. The range of new bone formation was 5.36% (6 mo) to 43.68% (12 mo). Residual HA graft particles were evident in all specimens, and the amount was inversely correlated with time. HA particles were often surrounded by an intense inflammatory infiltrate. DFDBA particles, largely present in the 6-month biopsy, were not recognizable in the 10-, 12-, and 13-month specimens, suggesting complete replacement. The combination of Osteograf/N and DFDBA appears to be osteoconductive and may be considered a valid alternative to autogenous bone grafts in sinus lift procedures. Histomorphometric and histologic evaluation may also be used to monitor the status of the future implant site.