OBJECTIVE The influence of bone augmentation of the floor of the maxillary sinus for the insertion of dental implants on sinus function has not been well investigated. In this study, the influence of the sinus lift on the development of maxillary sinus pathology was evaluated using generally accepted diagnostic criteria. METHODS A group of 45 patients in whom a sinus lift procedure had been performed were evaluated for sinus pathology 12 to 60 months after bone transplantation and implant insertion, using a questionnaire, conventional radiographic examination, and nasoendoscopy. RESULTS Postoperative maxillary sinusitis was detected in two of five patients with a predisposition for sinusitis, but in none of the other 40 patients. The occurrence of iatrogenic sinus membrane perforations during surgery was not related to the development of postoperative sinusitis in patients with healthy sinuses. CONCLUSIONS The occurrence of postoperative chronic sinusitis appears to be limited to patients with a predisposition for this condition. These predisposing factors need to be considered when evaluating patients for sinus lift procedures.