Sinus grafting procedures are a viable means of ensuring adequate bone for the placement of dental implants in the posterior maxilla. In the quest to improve predictability and accelerate the time line toward receiving a final prosthesis, researchers have turned to recombinant human proteins like osteogenic protein-1 for the potential to therapeutically enhance bone formation. Bilateral sinus augmentations were performed in 15 adult chimpanzees to evaluate treatment with different doses of the osteogenic protein-1 device or natural bone mineral (Bio-Oss). Methods of evaluation included soft tissue healing, radiography (computed tomographic scan), histology, residual l ateral wall defect surface area at 7.5 months, and the extent of soft tissue encleftation at 7.5 months. Findings revealed radiographic and histologic evidence of bone formation with all treatment groups and a statistically significant reduction in the depth of soft tissue encleftation and the residual lateral wall defect surfa ce area for both the Bio-Oss and the 2.5-mg osteogenic protein-1 per gram collagen matrix treatments when compared to collagen matrix alone. These results suggest that Bio-Oss and the 2.5-mg osteogenic protein-1 per gram collagen matrix effectively stimulate bone formation in the maxillary sinus.