The maxillary sinuses in 48 patients were grafted with dense, non-resorbable hydroxylapatite (HA) particles combined with autologous, cancellous bone. After 3 months of healing, HA-coated titanium endosteal implants were placed in the maxilla, and following an additional 3-5 month healing period, the dentitions were restored with various prostheses. Of the 267 maxillary implants placed, 18 (6.4%) failed. Thirteen (6.4%) of the 203 implants placed in the grafted floor of the sinus failed, and 5 (7.8%) of the 64 implants placed in the anterior maxilla failed. Simultaneous lateral and anterior onlay grafting of the alveolar process with the same composite graft material was required in 36 (75%) patients because the width of the alveolar process was considered insufficient for placement of endosseous implants. The mean follow-up period was 17 months (range 12-32). Results from this preliminary study indicate that composite grafting of the maxillary sinus with onlay grafting of the alveolar ridge will provide the bony structure necessary for placement of endosseous implants. Further follow-up of these patients is necessary to determine the long-term stability of this technique; however, these results are promising.