Peri-implantitis represent serious diseases after dental implant treatment, which affect both the surrounding hard and soft tissue. Due to high prevalence rate peri-implantitis can lead to the loss of the implant without multilateral prevention and therapy concepts. Early identification of sign and symptoms associated with peri- implantitis is necessary for better prognosis. Complete knowledge of aetiology associated with peri- implantitis will help in preventing the pathology. Hence; in the present review, we aim to highlight the aetiology and pathogenesis of peri-implantitis. Key words: Aetiology, Implant, Peri- implantitis.