Purpose: The purpose of this study was to determine the clinical parameters associated with long-term success and failure of single-tooth titanium plasma-sprayed (TPS) cylindric implants. Materials and Methods: Thirty-nine implants in 39 subjects were followed for 5 years. The following data were collected: subject age and gender, implant length, implant location, bone density, and implant position in relation to crestal bone. Assessments made at recall intervals included: Gingival Index (GI), probing depth, relative attachment level, and standardized radiographs. Failure was defined as a mean annual attachment loss rate (ALR) of >= 0.25 mm after the first year of implant function. Between-group differences were assessed nonparametrically using the Mann-Whitney and chi-square tests. Results: Nineteen implants were considered successes and 20 were considered failures with respective mean ALRs of 0.12 ¡À 0.07 mm and 0.42 ¡À 0.19 mm. The following factors were associated with success: longer implants (P .001), lower GI (P .001), higher bone density (P .0001), and implant position at the crest or supracrestally (P .0001). Age, gender, probing depth, and implant location were not related to outcome. Conclusions: A model using attachment loss as a parameter for success and failure has not been previously utilized. Longer implants, lower GI, higher bone density, and implant position at the crest or supracrestally were clinical factors associated with long-term success of single-tooth TPS cylindric implants in this patient population. Keywords: alveolar bone loss, attached gingiva, dental implants