The purpose of this study was to evaluate the clinical effectiveness of a connective tissue graft including periosteum used as a barrier for guided periodontal tissue regeneration in interproximal bony defects. An open flap debridement of a comparable interproximal bony defect in the same patient was used as a control. This study was performed at 2 different clinical centers. Six paired defects were treated at one center, and 16 paired defects at the other. Reentry surgeries were performed at 6 months. Preoperative comparisons of control and experimental sites with respect to clinical parameters and osseous measurements were similar. Post-surgical experimental sites produced more gain in clinical attachment (1.25 mm on buccal and 1.25 mm on lingual sites at center A and 1.26 mm on buccal and 1.18 mm on lingual sites at center B) and osseous defect fill (1.84 mm on buccal and 2.00 mm on lingual sites at center A and 1.66 mm on buccal and 2.04 mm on lingual sites at center B) when compared to control sites. The results of this trial indicate that clinical resolution of interproximal periodontal defects can be obtained with periosteal grafts used as barriers. J Periodontol 1998;69:1203–1209.