The purpose of this study was to evaluate the extent and predictability of periodontal regeneration with barrier membranes in deep infrabony defects. 25 patients(40% smokers) were included in this study. Fourty-one deep infrabony defects treated with membranes(PPD>6mm) were evaluated 1 year postoperatively following a plaque control regimen. Probing pocket depth(PPD), gingival recession(REC), and probing attachment level(PAL) were evaluated at baseline and postoperative 1 year. Plaque score at baseline was 16.2 and plaque score at 1 year was 9.9 A PAL gain of 4.1±-2.5mm along with a PPD reduction of 5.0±-2.3mm were observed. A PAL gain of 4.1±-2.5mm was observed at the smoking group and a PAL gain of 4.0±-2.5mm was observed at the non-smoking sroup. It was concluded that periodontal regeneration with membrane represented the predictable and effective treatment modality in the deep infrabony defects.