The goal of periodontal treatment is regeneration of the periodontium. Bone graft and absorbable PLA/PGA membrane have been used for this purpose. In this study, 4${ imes}$4mm 1-wall intrabony defects were surgically created bilaterally in the mandible of five male beagles. The control group went through a conventional flap operation, while the experimental group I was treated with absorbable PLA/PGA membranes only, group II was treated with absorbable membrane and calcium phosphate. The results are the following : 1. The defect height was 4.82${pm}$0.45mm in the control group, 4.93${pm}$0.79mm in the experimental I group, and 4.92${pm}$0.62mm in the experimental II group. There was no statistically significant difference among 3 groups(P <0.05). 2. The amount of junctional epithelium migration was 30.90${pm}$9.92% of the defect height in the control group, 39.16${pm}$7.51% in the experimental I group, and 38.68${pm}$12.22% in the experimental II group. There was no statistically significant difference among 3 groups(P <0.05). 3. The amount of connective tissue adhesion was 36.38${pm}$9.03% in the control group, 14.73${pm}$3.93% in experimental I group, and 27.87${pm}$9.70% experimental II group. Experimental group I was a statistically significantly different from control group(P <0.05). 4. The amount of new cementum regeneration was 32.92${pm}$10.51%, 50.04${pm}$7.61%, and 39.62${pm}$12.14% for the control, experimental I, and experimental II group respectively. Experimental group I was a statistically significantly different from control group(P<0.05). 5. The amount of new alveolar bone regeneration was 27.24${pm}$7.49%, 40.75${pm}$8.03%, and 36.47${pm}$15.11% for the control, experimental I, and experimental II group respectively. Experimental group I was a statistically significantly different from control group(P <0.05). The results suggest that the use of PLA/PGA membrane in 1-wall intrabony defect of beagle dogs may promote periodontal regeneration. Further studies are required to determine their regeneration effects.