The aim of the present study was to evaluate whether new attachment, gained following guided tissue regeneration (GTR) therapy, can be maintained over longer periods of maintenance therapy. 88 sites at 52 teeth with various types of periodontal defects in 39 patients were treated with the GTR procedure during the period 1984-1989. The effect of treatment was evaluated by assessing probing attachment level (PAL) prior to surgery and 6 months post-surgery. Only sites which at the 6-month examination (baseline) had gained 2 mm or more of PAL were regarded as successfully treated and scheduled for further monitoring. At baseline, 80 sites could be identified which fulfilled this criterium. Of the 80 new attachment sites, all have been monitored for 1 year, 65 for 2 years, 40 for 3 years, 17 for 4 years and 9 sites for 5 years. The results demonstrated that the attachment gain, obtained as the result of the GTR treatment, could be maintained over periods up to 5 years.