Introduction. Many studies describe the necessity of using grafting materials in case of lateral sinus floor elevations. Besides the advantages of it, an important role plays the autogenous bone which is often mixed with xenograft or synthetic materials in order to achieve a better quality tissue. However, these methods are often related to complications like sinusitis or failures.   Aim of the study. To appreciate the endo-sinus bone gain in case of lateral sinus floor elevation with immediate implants placement without any grafting material.   Materials and methods. The study was axed on 5 patients (mean age 38.23±3.12 years) who received 12 implants in posterior sides of upper jaw. The implants insertion was performed simultaneously with lateral sinus floor elevation using the trap door technique. Before implants insertion the sinus cavity formed after elevation were filled only with blood collected from peripheral vein. After suturing, platelet rich plasma was injected from buccal aspects. Six months later, the second surgical step was performed, and the prosthetic treatment was performed after another 4 weeks. Periimplant bone loss as well as endo- sinus bone gain during healing and 1 year postprosthetic has been evaluated. Statistical analysis was made by calculating mean values, standard errors and Pearson correlation test.   Results. All implants successfully integrated. Residual bone height from mesial and distal aspects was 5.96±0.4mm and 5.05±0.21mm, while the length of implants protruded into sinus were 5.81±0.35mm and 6.15±0.19mm respectively. At the end of healing period, the endo-sinus bone gain consisted 7.38±0.402mm (mesial) and 8.17±0.11mm (distal), but radiographically it had a lower opacity than the native one. One year later, the bone became mature with good corticalization of the new sinus floor, with dimensions of 5.93±0.56mm and 6.65±0.087mm from mesial and distal aspects. During this period, a shrink of 1.45±0.16mm and 1.51±0.19mm occurred. The cortical periimplant bone loss around implants from mesial and distal aspects was: 0.23±0.086mm and 0.21±0.043mm during healing; 0.4±0.12mm and 0.68±0.07mm during 1 year A strong correlation between implant protruded length and endo-sinus bone gain was observed: 0.92 and 0.682 (from mesial and distal aspects).   Conclusions. In appropriate conditions, the lateral sinus floor elevation without grafting material and with simultaneously implant placement lead to formation of an adequate amount of endo-sinus bone. By this way, it is possible to avoid the use of grafting materials. However, more studies and longer follow-up periods are necessary in order to appreciate the limits and indications of this method.