This prospective longitudinal 3-year study compared clinical parameters and implant success rates of removable superstructures supported by both teeth and implants in patients with treated generalized aggressive periodontitis (GAP) and of cemented, implant-retained fixed superstructures in periodontally healthy patients. A total of 17 partially edentulous patients with 54 implants took part in the study. Nine patients with treated GAP received removable superstructures according to the Marburg double crown system, and eight periodontally healthy patients received fixed superstructures. Teeth were examined 2 to 4 weeks before extraction of the nonretainable teeth (baseline) and 3 weeks after insertion of the definitive abutments. Every 3 months over a 3-year period, clinical parameters were recorded and the composition of the subgingival microflora was determined. Intraoral radiographs were obtained at baseline, just after insertion of the superstructure, and 1 and 3 years later. Both groups showed mean plaque and gingival indices below 0.43 at implants and teeth. Mean probing depths around implants increased by approximately 0.7 mm and remained virtually constant for the teeth. Mean attachment loss at implants was 0.9 mm in GAP patients and 0.5 mm in healthy patients. The morphologic distribution of microorganisms in both groups showed healthy conditions. Moderate bone loss at teeth and implants was registered. Implant success rates were 100% in the healthy patients and 97.6% in the GAP patients. No significant differences were seen in the results between the groups.