Purpose: The aim of this prospective randomized study was to compare the clinical accuracy of and surgical time required for mandibular dental implant placement with 2 computer-assisted navigation systems using pre- and postoperative computerized tomographic (CT) data. Materials and Methods: In 16 patients with edentulous mandibles, 4 interforaminal implants per patient were placed with computer-assisted navigation. The implant bed was prepared by transmucosal drilling without mucosal punching. Patients were randomly allocated to either the VISIT navigation system (32 implants; 8 patients) or the Medtronic StealthStation Treon navigation system (32 implants; 8 patients). Pre- and postoperative CT scans were matched using the normalized mutual information 3D registration algorithm to compare preplanned and final implant positions. Operation room time was recorded from start of preoperative preparations to end of surgery. Results: All implants were placed as planned; there were no intra- or postoperative complications. Average implant deviation errors of 0.7 mm and 0.9 mm were recorded for the VISIT and StealthStation Treon navigation systems, respectively. Timing revealed an average operation room time of 81.3 ± 15.8 minutes for the VISIT navigation system and 60 ± 10.4 minutes for the StealthStation Treon navigation system. Conclusions: The accuracy of implant bed preparation and placement was similar in both systems. Both navigation systems are equally precise in a clinical environment. However, total operation room time was 25% shorter with the StealthStation Treon navigation system, probably because of the faster tracking system update rate. (Controlled Clinical Trial) Schlagwörter: accuracy, computer-assisted navigation, dental implants