This study reports the incidence of complications and sinus membrane perforations when using sonic instruments to prepare the lateral window osteotomy for maxillary sinus augmentation. The charts of 33 consecutive patients (40 sinuses) were reviewed. Sinus membrane perforations were reported in 7 cases (17.5% of procedures), with 3 perforations occurring during preparation of the osteotomy window (7.5% of procedures). Postoperatively, 2 cases of sinus infection (5%) and 2 cases of flap dehiscence (5%) were recorded. This study demonstrates that elevation of the sinus floor with a combination of hand and sonic instruments is feasible and safe, with a limited incidence of complications. (Int J Periodontics Restorative Dent 2014;34:105-112. doi: 10.11607/prd.1387)