The risk of developing peri-implantitis seems to be more pronounced in patients with a history of periodontitis. Pretreatment to eliminate periodontal pathogens from the patient's oral cavity before dental implant treatment therefore is important to reduce the risk of peri-implantitis. Smoking has been shown to be a negative risk factor for treatment success. Several protocols have been used in the treatment of peri-implantitis. Mechanical infection control following surgical flap procedures, particularly in conjunction with antimicrobial therapy, is the most successful concept. There is no reliable evidence that suggests which intervention is the most effective for treating peri-implantitis. This article includes background information on the biology of tissue-destructive periodontitis and peri-implantitis to help clinicians interpret the clinical manifestation of the risk for peri-implantitis.