Clinical healing following guided tissue REGENERATION (GTR) in intrabony pockets using a polyurethane membrane was compared to healing following gingival flap surgery (GFS).Ten patients with adult periodontitis and the presence of intrabony defects were selected. Oral hygienic treatments were performed during a 4- week's period prior to surgery.One intrabony defect on each patient was randomly chosen to be treated according to the guided tissue REGENERATION (GTR) procedure. The other side received the control treatment GFS. Test group received the GTP treatment including polyurethane membrane after reflecting the flap and curettage of defect. However, flap surgery and curettage were done in control group.The patients were evaluated for changes in probing depth (PD), clinical attachment level (CAL), recession changes in crystal resorting, and defect bone fill. Clinical examinations were performed again 6 months post operatively.The average of (PD), (CAL) and defect depth (DD) before surgery in test group was 3.23, 13.87 and 7.3 mm respectively and in control group was 3.1, 8.9, 7.4 mm. After 6 months the average of (PD), (CAL) and (DD) was 1.69, 1.68, 3.5 mm, respectively and in control group was 1.24, 1.09, and 2.90 mm. Test group and control group showed successful results in treatment of intrabony defects. Test group showed better results than control.No significant difference was observed between two treatment procedures from the point of view of pocket depth reduction, attachment gain, and recession.The bony fill and crystal resorption results suggest similar clinical potential of GTR procedures compared to GFS in treatment of intrabony pocket. However, in order to gain future insight, larger samples and longer observation periods should be evaluated.