Purpose: To review the literature on clinical, radiographic, and biochemical parameters used for monitoring peri-implant conditions. Materials and Methods: A MEDLINE search was conducted that included articles published in English until the end of August 2003. Results from human and experimental animal studies are presented. Results: The parameters that may be used to assess the presence of peri-implant health and the severity of peri-implant disease include plaque assessment, mucosal conditions, peri-implant probing depth, width of the peri-implant keratinized mucosa, peri-implant sulcus fluid analysis, suppuration, implant mobility and discomfort, resonance frequency analysis, and radiographic evaluation. Discussion: Based on the analysis of the available evidence, it appears reasonable to use a number of clinical and radiographic parameters to discriminate between peri-implant health and disease. Conclusions: Systematic and continuous monitoring of peri-implant tissues during maintenance care is recommended for the early diagnosis of peri-implant disease.