The present study was designed to compare recombinant human bone morphogenetic protein-2 (rhBMP-2) impregnated on an absorbable collagen sponge (ACS) with particulate cancellous bone and marrow (PCBM) harvested from the iliac crest in an animal model of maxillary sinus floor augmentation. Bilateral sinus floor augmentation procedures were performed in 30 adult Japanese white rabbits. rhBMP-2/ACS or PCBM was grafted to each maxillary sinus. Animals were sacrificed at 2, 4, or 8 weeks after grafting, and bone formation in response to each implant was evaluated histologically and histometrically. Histometric results compared by analysis of variance revealed no statistically significant difference in the bone volume at augmented areas between the two types of implant (P > 0.05). Histologic evaluation documented that the trabeculae with a lamellar structure were embedded in fatty marrow at 8 weeks in both implant sites. These results suggest that sinus floor augmentation with rhBMP-2/ACS or PCBM induces comparable histologic and histometric evidence of bone formation in rabbits.