Purpose: The objective of this study was to evaluate sinus floor augmentation with simultaneous implant placement using platelet-rich fibrin (PRF) as the only grafting material. Materials and Methods: This study included patients who underwent sinus floor augmentation with simultaneous implant placement using PRF as the sole filling material between July 2009 and January 2011 at the Department of Oral and Maxillofacial Surgery, Nagasaki University Hospital. For each patient, presurgical and postsurgical (6 months after the surgery) radiography and computed tomographic scanning were performed to assess bone formation at the implant sites. The density (in Hounsfield units [HU]) of the newly formed bone and the bone height from the sinus floor to the alveolar crest where implants were inserted were measured using implant planning software (Simplant, Materialise Dental). Results: Nine sinus floor augmentations were performed, and 17 implants were placed in six patients. The mean residual bone height between the sinus floor and alveolar crest was 4.28 ± 1.00 mm (range, 1.9 to 6.1 mm) prior to surgery and 11.8 ± 1.67 mm (range, 9.1 to 14.1 mm) after surgery. The alveolar bone ridge was wide enough for implant placement in all cases. The mean density of the newly gained bone around the implants was 323 ± 156.2 HU (range, 185 to 713 HU). All implants were clinically stable at the time of abutment insertion, 6 months after sinus augmentation. Conclusion: Sinus elevation with simultaneous implant placement using PRF as the only filling material may promote natural bone regeneration. Keywords: bone regeneration, dental implants, Hounsfield index, maxillary sinus, platelet-rich fibrin, resonance frequency analysis, sinus grafting