Purpose: Recently, histologic studies in the beagle dog model demonstrated that CO2 laser-assisted implant decontamination can result in reosseointegration. Consequently, the purpose of this study was to assess the efficacy of CO2 laser-assisted therapy as compared with conventional therapy, with the concomitant use of b-tricalcium phosphate, in humans. Materials and Methods: The study included 32 patients with 73 ailing implants. In the laser group, 22 implants were treated with soft tissue resection following laser decontamination; whereas in 17 implants, bone augmentation was performed. In the control group, soft tissue resection after conventional decontamination was performed in 19 implants, augmentation in 15 implants. Results were evaluated 4 months after surgery and in May 2004. Results: Four months after therapy, there were no significant differences in distance from implant shoulder to the first bone contact (ie, DIB values) between implants undergoing laser decontamination and soft tissue resection and implants treated with conventional decontamination followed by soft tissue resection. At the end of the study, there was a statistically significant difference between these 2 groups. Four months after therapy, DIB values after laser decontamination and augmentation were significantly more favorable than after conventional decontamination and augmentation. This difference was no longer detectable at the end of the study. Conclusion: Based on the results of this study, it may be concluded that the treatment of peri-implantitis may be accelerated by using a CO2 laser concomitant with soft tissue resection. However, with respect to long-term results in augmented defects, there seems to be no difference between laser and conventional decontamination. Keywords: CO2 laser, guided bone regeneration, peri-implantitis