9 sites of 8 teeth in 5 adults with severe periodontitis were treated by open surgical debridement followed by placement of 1 of 2 Teflon barrier membranes. Teeth were notched at both gingival margins and deepest visible calculus on the root. Barrier membranes were placed apical to alveolar crest and coronal to gingival notch. Flaps were sutured coronally and patients were placed on 1.2% chlorohexodine gluconate twice daily for 2 weeks, post-surgery. Subsequent to suture removal, patients returned for frequent plaque control until block removal. In order to observe early healing responses, 6 sites were harvested 5 to 8 weeks after surgical treatment. 3 additional sites were removed 14, 22 and 30 weeks respectively after surgical treatment. Histologically, new cementum was seen in a linear direction along root surfaces in 6 out of 9 sites (length of cementum = 0.5 to 1.7 mm). 3 sites showed no evidence of new attachment. At sites of cementogenesis, functionally-oriented fibers were inserted. The osseous seams opposite the new attachment often demonstrated osteogenesis. Regenerative responses were seen with both types of teflon membranes and were present as early as 5 weeks after surgery.