Purpose: The present study compared the regenerative outcome of sinus graft procedures in a group of patients who underwent the repair of an intraoperatively diagnosed sinus membrane perforation to that of a group of patients without sinus membrane perforations. Materials and Methods: A sinus floor augmentation procedure was performed in 73 sinuses in 63 patients. In 28% of these sinuses a significant (> 5 mm) membrane perforation was observed intraoperatively. In these cases, the perforation was sealed with a freeze-dried human lamellar bone sheet, and the grafting procedure was carried out as planned. The following parameters were measured on panoramic radiographs immediately postoperatively and at the 6- and 24-month follow-up examinations: (1) the distance between the occlusal edge of the implant and the preoperative sinus floor, (2) the distance between the occlusal edge of the implant and the postoperative sinus floor, and (3) the distance between the occlusal edge of the implant and the alveolar crest. Results: The patients whose sinus membranes were perforated experienced no complications. No statistically significant differences were found between the 2 groups in the parameters measured. Discussion: Lambone was used in all cases in the present study. In no case did the sinus augmentation procedure have to be abandoned. Conclusion: It can be concluded that membrane elevation must be carefully executed to avoid membrane perforation, but that if it occurs, it is still possible to continue the procedure safely after repair.