Placement of endosseous implants in the atrophic maxilla is often limited because of a lack of supporting bone. A technique to augment the floor of the maxillary sinus with autogenous bone graft seems to be a new reliable treatment modality. The morbidity and complication rate of augmentation of the maxillary sinus floor was studied in 75 patients. The sinus floor was augmented with iliac crest (n = 65, 128 sinuses, 276 implants), mandibular symphysis (n = 8, ten sinuses, 21 implants), or maxillary tuberosity grafts (n = 2, two sinuses, two implants). The width of the alveolar crest had to be reconstructed in 52 patients, while in the other 23 patients augmentation and implantation were performed simultaneously. Perforation of the sinus membrane occurred in 45 patients, but this did not predispose them to the development of sinusitis. Loss of bone particles and sequesters were observed in one (diabetic) patient only, in whom a mucosal dehiscence occurred. A second augmentation procedure was successful. Symptoms of transient sinusitis were observed in two of the seven patients with a predisposition for sinusitis. These symptoms were successfully treated with decongestants and antibiotics. One patient developed a purulent sinusitis which resolved after a nasal amrostomy. The bone volume was sufficient for insertion implants in all patients. Twenty of 299 patients (6.7%) in whom Brånemark implants had been inserted were lost to follow-up (mean, 32 months); no sinus pathology was observed. The patients received implant-supported overdentures (58 patients) or fixed bridges (17 patients) and experienced no complaints with regard to the grafts or implants. We conclude that the morbidity and complication rate of bone grafting of the floor of the maxillary sinus floor with autogenous bone is low.