Purpose: In patients with atrophic mandibles, elevation of the floor of the mouth often prevents intraoral rectangular radiography for longitudinal follow-up studies, while extraoral techniques such as panoramic radiographs tend to produce distorted views of the interforaminal region. In this study, intraoral rectangular radiographs and panoramic radiographs were compared for their accuracy in evaluating peri-implant bone loss. Materials and Methods: In a recall program, 22 patients with 88 screw-type implants (44 MKII and 44 Frios) were followed. Interforaminal marginal bone loss was evaluated by extraoral orthopantomograms and by intraoral rectangular radiographs. In addition, pocket depth, Periotest readings, and bleeding on probing were recorded. For statistical analysis, the Spearman coefficient of correlation was used. The effects on bone loss and clinical variables were computed with a mixed model and the Bland and Altman method. Results: Computed as least square means, the mean difference between panoramic radiographs (2.4 ± 0.2 mm for MKII implants and 1.6 ± 0.2 mm for Frios implants) and intraoral radiographs (2.6 ± 0.2 mm and 1.4 ± 0.2 mm, respectively) was 0.2 mm (range, 0.1 to 0.8 mm). Discussion: In this study, the 2 imaging techniques were comparable clinically in terms of the precision with which they could be used to measure marginal bone loss. Conclusion: For highly atrophic mandibles with unfavorable imaging conditions, rotational panoramic radiographs can be a useful alternative to intraoral small-format radiographs for evaluating periimplant bone loss.