Fifteen patients, men and women aged 18 to 65 years, were treated for periodontitis. Each patient had at least two bilateral intrabony defects; one was designated the experimental site and the other the control site. Both sites were surgically debrided, but one osseous defect received an HTR polymer implant. Patients were followed for 12 months postoperatively. Maximum pocket reduction occurred within 2 months of initial therapy in both experimental and control sites. Initially, pocket reduction was significantly greater in implanted sites than in control sites, but this difference did not occur subsequently. At the end of the 12 months, pocket reduction responses were similar at control and implanted sites.