Alveolar bone resorption and pneumatization of the maxillary sinus after the extraction of teeth limits the quantity and quality of the bone necessary for successful implant placement, especially in the edentulous posterior maxilla. To overcome these problems, sinus floor elevation procedure is used and this is divided into lateral approach and trans-crestal approach by surgical approach method. Trans-crestal approach is less invasive and it has a less post operation swelling, shorter operation time and shorter healing period as contrasted with a lateral approach. The aim of this study is to evaluate the survival rates and analyze the stability of trans-crestal approach. 250 partially or completely edentulous patients who have been treated in Livingwell dental hospital between 2003 to 2009 with atrophic maxillary posterior were selected. The osteotome technique and sinus drill technique method were used for sinus floor elevation procedure. A total of 414 implants-Tapered Screw Vent implant(Zimmer, USA), Pitt-Easy implant(Oraltronics, Germany), Spline implant(Zimmer, USA)-were placed in grafted maxillary sinus. The autogenous bone or a combination with the allograft or alloplast was grafted into sinus mainly. And sinus floor elevation was combined with vertical/horizontal onlay bone grafts to reconstruct the defect of alveolar ridge. The mean period to load implants was 24 weeks. Panoramic radiographs were taken preoperatively, postoperatively (1day after operation), after prosthesis placement, and then at yearly intervals for evaluate the peri-implant bone and maxillary sinuses. The average preoperatively height of the maxillary alveolar bone was 7.09±1.49mm. 10 implants failed during the healing period and 1 implant failed after prosthetic loding. A total survival rate(97.3%) of trans-crestal approach was similar to result of the study which showed survival rates(97.8%) of lateral approach technique that was reported - Ho Yeol, Jang et al. The Korean academy of implant dentistry, Vol.27, No.1, 2009 - by our hospital. The results indicate that the trans-crestal approach method to elevate maxillary sinus floor is a acceptable method at atrophic maxillary posterior area. [THE JOURNAL OF THE KOREAN ACADEMY OF IMPLANT DENTISTRY 2010;29(1):1-9]