INTRODUCTION: Our aim in this investigation was to evaluate and compare orthodontic anchorage capacity of 4 anchorage systems during leveling/aligning and space closure after maxillary premolar extractions. METHODS: One hundred twenty patients (60 girls, 60 boys; mean age, 14.3 years; SD 1.73) were recruited and randomized into 4 anchorage systems: Onplant (Nobel Biocare, Gothenburg, Sweden), Orthosystem implant (Institut Straumann AG, Basel, Switzerland), headgear, and transpalatal bar. The main outcome measures were cephalometric analysis of maxillary first molar and incisor movement, sagittal growth changes of the maxilla, and treatment time. The results were also analyzed on an intention-to-treat basis. RESULTS: The maxillary molars were stable during the leveling/aligning in the Onplant, Orthosystem implant, and headgear groups, but the transpalatal bar group had anchorage loss (mean, 1.0 mm; P <.001). During the space-closure phase, the molars were still stable in the Onplant and Orthosystem groups, whereas the headgear and transpalatal bar groups had anchorage loss (means, 1.6 and 1.0 mm, respectively; P <.001). Thus, the Onplant and the Orthosystem implant groups had significantly higher success rates for anchorage than did the headgear and transpalatal bar groups. Compared with the Orthosystem implant, there were more technical problems with the Onplant. CONCLUSIONS: If maximum anchorage is required, the Orthosystem implant is the system of choice.