Bone resorptive patterns may prevent the ideal placement of endosseous implants. Numerous techniques have been described to create a more favorable surgical site for implant placement. This retrospective review was conducted to determine the frequency of need for implant site preparation in an outpatient clinical setting. In addition, different techniques of surgical site preparation were evaluated to determine their frequency of use and surgical outcome. A history review was conducted of all consecutively treated partially edentulous patients between January 1993 and December 1997. This review evaluated the number of implants placed, the age and gender of the patient, the type of graft used, and the status of the implant. In all, 542 patients were seen in this time interval, with a total of 1,313 implants placed. Implant site preparation was needed in 4.4% of the patients, with the requirement for grafts occurring more frequently in the maxilla. Implant site preparation is a relatively infrequent requirement in the general population. Grafts are required more frequently in the maxilla than in the mandible. Complications following grafting were relatively infrequent and were not severe. Parole chiave: grafting, implants, outcome assessment, site preparation