Purpose: To evaluate the outcome of dental implants placed in partially edentulous patients with a history of severe periodontitis (SP), moderate periodontitis (MP) and no periodontitis (NP). Materials and methods: Sixty-two partially edentulous patients were consecutively enrolled in this study. Patients were divided into three groups according to their initial periodontal conditions, assessed with a modified Periodontal Screening and Recording (PSR) index: 26 patients were in the SP group, 7 in the MP group, and 29 in the NP group. Patients requiring periodontal treatment were treated prior to implantation. Various dental implants and procedures were used. In the SP group 129 implants were placed, 26 were placed in the MP group, and 72 in the NP group. Outcome measures were prosthetic success, implant survival, prevalence of peri-implantitis and mean peri-implant bone level changes on periapical radiographs. Results: Six patients dropped out, two from each group, at 5 years. Two implants and their prosthesis failed with peri-implantitis in one patient and two implants were successfully treated for periimplantitis in another patient in the SP group. After 5 years, patients affected by SP and MP lost on average twice the amount of peri-implant bone compared with healthy patients (2.6 mm versus 1.2 mm). This difference was highly statistically significant. Conclusions: Patients with a history of SP and MP lose more peri-implant bone than periodontally healthy patients and might be at higher risk for peri-implantitis and implant failures. Schlagwörter: bone level, dental implant, peri-implantitis, periodontitis, prognosis