This investigation was designed and implemented as a single-center, prospective study to evaluate the clinical response to the Laser-Assisted New Attachment Procedure (LANAP). Eight patients with advanced periodontitis were enrolled and treated with full-mouth LANAP therapy and monitored for 9 months. Fullmouth clinical measurements, including clinical attachment level (CAL), probing depth (PD), and recession, were provided at baseline and after 9 months of healing by a single calibrated examiner, including a total of 930 sites and 444 sites with initial PD equal to or greater than 5 mm. Clinical results for the 930 sites measured pre- and postoperatively revealed that mean PD was reduced from 4.62 ± 2.29 mm to 3.14 ± 1.48 mm after 9 months (P .05). CAL decreased from 5.58 ± 2.76 mm to 4.66 ± 2.10 mm (P .05) and recession increased from 0.86 ± 1.31 mm to 1.52 ± 1.62 after 9 months (P .05). For the subset of 444 sites with initial PD greater than or equal to 5 mm, the PD decreased from 6.50 ± 2.07 mm to 3.92 ± 1.54 mm (P .05) and CAL decreased from 7.42 ± 2.70 mm to 5.78 ± 2.06 mm (P .05). As demonstrated by the clinical evaluation, the majority of treated sites demonstrated clinical improvement. LANAP therapy should be further investigated with long-term clinical trials to compare the stability of clinical results with conventional therapy. (Int J Periodontics Restorative Dent 2014;34:21-27. doi: 10.11607/prd.1848)