The present blinded, randomized, controlled investigation histomorphometrically evaluated the vital bone formed following bilateral grafting with two different materials--Puros, a mineralized cancellous bone allograft (MCBA), and Bio-Oss, an anorganic bovine bone matrix (ABBM)--at 26 to 32 weeks following graft placement. Thirteen patients were selected who required bilateral sinus augmentation. Following elevation of the lateral sinus walls, one material was placed in the right sinus and the other in the left sinus, as determined by randomized choice. Twenty-six to 32 weeks after grafting (the same time frame was used for each individual patient), a trephine core was taken from the previously elevated lateral wall area and sent for histomorphometric analysis. Cores were obtained from 22 healed sinus augmentations in 11 patients. Eight patients provided bilateral cores, two patients had intact MCBA cores but inadequate ABBM cores, and another patient had an intact ABBM core but an inadequate MCBA core. Histomorphometric analysis of 10 MCBA cores and 9 ABBM cores revealed average vital bone content of 28.25% and 12.44%, respectively. The average percentage of residual nonvital bone was 7.65% in the MCBA cores and 33.0% in the ABBM cores. Significantly more bone was formed in the MCBA sites (n = 8 patients, paired t test). Histologically, both MCBA and ABBM particles were surrounded by new bone, osteoid, and osteoblasts. A higher average percentage of new vital bone was seen around the MCBA particles than around the ABBM particles.