Guided tissue regeneration(GTR) is regenerative operating technique at dental clinic. The vertical bone defect can be treated by GTR. The purpose of this study is to present the importance of GTR at dental clinic. The vertical bone defect was observed on distal side of mandibular right 2nd molar. The patient had been treated scaling, root planing and GTR. Both nonresorbable occluding membrane and resorbable occluding membrane can be used as GTR operation. The former was used in this study. Nonresorbable occluding membrane can exclude epithelial cells from healing defect. The Bio-Oss bone graft used at GTR operation. A radiograph demonstrates that the regenerative part was observed by GTR. In conclusion, GTR operating effect has importance on vertical defect at dental clinic.