Purpose: To review the literature on the treatment of peri-implant diseases. Specific emphasis was placed on the use of antimicrobial therapy, defined as local or systemic administration of antiseptic and/or antibiotic agents. Materials and Methods: A search of MEDLINE, the Cochrane Controlled Trials Register, and The Cochrane Health Group Specialized Register was conducted, and articles published in English until July 31, 2003, were included. The results of experimental animal studies and human research are presented. Results: A variety of antimicrobial treatment regimens in combination with nonsurgical or surgical debridement with and without regenerative therapy were reported. Use of antimicrobials varied between studies with respect to type of drug, dosage, delivery system, duration, and commencement of antibiotic administration. Patient compliance and adverse effects related to the antimicrobials were mostly not mentioned. Discussion: While the majority of the case reports and studies presented showed positive outcomes following antimicrobial treatment, there were no nonmedicated controls included, so the relative effect of the antimicrobial agent(s) cannot be evaluated. Conclusions: Although antimicrobials are widely used for the treatment of peri-implant diseases, evidence of their benefit is limited, and randomized, controlled human trials should be initiated where ethically possible. In addition, prospective cohort studies designed to monitor consecutive cases treated using specific treatment protocols are required.