Recently, more and more clinical cases of peri-implantitis for which surgical therapy is indicated have been reported. Ideal diagnostic modalities, prevelance, indicated therapy, and prognosis for peri-implantitis are still investigated. Scientific evidence of surgical therapy for peri-implantitis are not enough for now, and should be obtained from well-designed, long-term clinical studies in the future. When the surgical approach is applied for peri-implantitis, long-term prognosis of the surgical therapy should be kept in mind and importance of maintenance therapy also have to be emphasized.