This study aims to investigate the clinical outcome following treatment of peri-implantitis lesions. Five subjects with 7 implants were treated with surgical approach. Four subjects with 6 implants were initially treated with non-surgical approach or hygiene control. However, inflammation was not resolved and more bone loss was found. Therefore, surgical treatment was performed. After surgical exposure of the defect, granulation tissue was removed and implant surface was treated using tetracycline and chlorhexidine. Then, the flaps were sutured. The wound healing was performed in a non-submerged mode. The present finding demonstrates stable results without progression of bone loss. In one subject, deep V shaped bone defect was filled with bone substitute (ICB, CanCellous Bone, Rockey Mountain Tissue Bank, USA), and resorbable membrane (Lyoplant$^{(R)}$, B.Braun Aesculap AG, Germany) was placed over the grafted defect and healing abutment was connected. However, the inflammation was not resolved and more bone loss was found. At one month after regenerative surgery, the implant was removed.