Aim: To evaluate the outcome of dental implants placed in patients with a history of periodontitis. Patients with no or mild history of periodontitis served as controls. Materials and methods: A total of 1727 patients were consecutively treated in four private practices. Patients were divided into three groups according to their initial periodontal conditions assessed with a modified periodontal screening and recording (PSR) index: 630 patients were in the severe periodontitis (SP) group, 839 in the moderate periodontitis (MP) group, and 258 had no periodontitis (NP). Patients requiring periodontal treatment were treated prior to implantation. Various implant systems and procedures were used. In total, 3260 implants and 1707 implantsupported prostheses were placed in the SP group, 2813 implants and 1744 implant-supported prostheses in the MP group, and 647 implants and 424 implant-supported prostheses in the NP group. Mixed implant-tooth supported prostheses (98 prostheses in 89 patients) were not considered. Outcome measures were prosthesis and implant survival. Results: Two-hundred and fifty patients were lost to follow-up 5 years after loading. Regarding prosthesis failures, 13 prostheses could not be placed or failed in 13 patients of the SP group (0.8%), 11 prostheses could not be placed or failed in 9 patients of the MP group (0.7%), and 3 prostheses failed in 3 patients of the NP group (0.9%). For implant failures, 130 (4.5%) implants failed in the SP group, 74 (3.1%) implants failed in the MP group, and 15 (3.0%) implants failed in the NP group. Most of the implant failures (90%) occurred before implant loading. Fitting a logistic regression for early implant failures and total implant failures, taking into account the clustering of implants in patients, there were no statistically significant differences between the three PSR groups (P > 0.05). Conclusions: Owing to the retrospective nature of this study, conclusions need to be interpreted with caution. A previous history of periodontal disease may not have a significant impact on implant failures up to 5 years after loading. Keywords: dental implants, periodontitis, prognosis