Purpose: This study was undertaken to evaluate clinically, histologically, and immunohistochemically the use of a new porous hydroxyapatite (HA) (B. Agra, Cabon, Milan, Italy) as a grafting material for maxillary sinus augmentation with simultaneous implant placement. Materials and Methods: A total of 28 titanium implants were placed in 12 patients with an average of 4.5 mm of bone on the sinus floor. HA granules were packed around the implants in the sinus cavity. After a healing period of 5 to 6 months, second-stage surgery was carried out. In 5 patients, bone cores were harvested from grafted areas and processed for histology and immunocytochemistry. Results: All implants were clinically stable at second-stage surgery and were followed for an average of 3 years. The histology showed newly formed bone in direct contact with the HA granules. Immunohistochemistry showed the presence of large quantities of bone sialoprotein and osteopontin in and around the granules of HA. Discussion and Conclusion: This study suggests that a new porous HA accommodated sinus floor augmentation in patients with 3 to 5 mm of bone height preoperatively. By possibly attracting circulating biocomponents at sites of tissue repair, it may promote bone regeneration.