This study assessed the efficacy of augmentation grafting of the maxillary sinus with simultaneous placement of dental implants in patients with less than 5 mm of alveolar crestal bone height in the posterior maxilla prior to grafting, although the procedure has traditionally been contraindicated based on empirical data. A total of 160 hydroxyapatite-coated implants was placed into 63 grafted maxillary sinuses in 63 patients whose crestal bone height in this region ranged from 3 to 5 mm. Patients were followed for 2 to 4 years after the placement of definitive prostheses. There were no postoperative sinus complications. Following uncovering of the implants at 9 months after surgery, there was no clinical or radiographic evidence of crestal bone loss around the implants. Histologic examination of bone cores from the grafted sites revealed successful integration and a high degree of cellularity. All patients maintained stable implant prostheses during follow-up. These findings indicate that the single-step procedure is a feasible option for patients with as little as 3 mm of alveolar bone height prior to augmentation grafting, utilizing hydroxyapatite-coated implants and autogenous bone. Keywords: atrophic maxilla, bone graft, dental implants, sinus augmentation, sinus mucosa