This study evaluated a bovine-derived bone xenograft (Bio-Oss) in the treatment of human periodontal osseous defects. Four patients with at least one tooth that had been recommended for extraction because of interproximal advanced periodontal disease volunteered to participate. The surgical procedure consisted of flap reflection, soft tissue debridement, placing a notch in calculus as a histologic reference point, root planing, placement of the bovine-derived xenograft and a bioresorbable physical barrier, and flap closure. Patients were seen every 2 weeks for plaque control and any necessary adjunctive treatment. At 4 to 6 months postsurgery, 6 teeth, along with the adjacent graft site, were removed en bloc. Histologic observations demonstrated new bone, new cementum, and new periodontal ligament coronal to the reference notch in 3 of the 4 specimens. This study indicates that periodontal regeneration is possible following grafting with a bovine-derived xenograft.