Aim:To evaluate the stability of attachment achieved in infrabony defects by regenerative treatment over 60 ± 12 months compared to control teeth. Methods:Patients treated regeneratively in at least one infrabony defect between 2004 and 2010 were screened for this retrospective cohort study. Complete examinations available for baseline, 12 and 60 ± 12 months after surgery, and a respective control tooth without treatment, provided eligibility for analysis. Results: Twenty-seven patients (age 58 ± 11.7 years; 12 females, five smokers) were included, each contributing one infrabony defect and one control tooth. Regenerative therapy resulted in significant attachment gain (2.7 ± 1.6 mm; p < 0.001) after 1 and (3.0 ± 2.2 mm; p < 0.001) 5 years. Control teeth were stable (vertical probing attachment level [PAL-V] change: 1 year: 0 ± 0.8 mm; 5 years: −0.2 ± 1.2 mm). The study did not detect any significant change of PAL-V from 1 to 5 years after surgery for regenerative (−0.3 ± 2.4 mm) and control teeth (−0.2 ± 1.4 mm). Multivariate analysis associated smoking and generalized recurrence of periodontitis (amount of sites with PPD > 5 mm) with attachment loss. Conclusions: PAL-V achieved by regenerative therapy in infrabony defects is as stable over 5 years as periodontally reduced but gingivally healthy or gingivitis sites. Smoking and periodontitis recurrence are associated with attachment loss. K E Y W O R D S guided tissue regeneration, operative, periodontal attachment loss, periodontitis, surgical procedures | 651 ABDUL RAHMAN et AL.