Sinus lift has been widely studied and is highly successful. The aim of this research was to establish the prevalence of intrasinusal septum in consecutive surgeries for maxillary sinus floor elevation and identify the relation with sinus membrane rupture. Ninety one surgeries were realized in patients with an indication for dental implant installation in the posterior maxilla; the patient with complete clinical and medical record (card, radiography, etc.) and without contraindications for the procedure was included in the study; the surgery was realized with local or general anesthesia and the material used for inlay graft was autogenous bone or biometarials. The septum was identified by panoramic image in the preoperatory and clinically at the time of surgery; any complication was studied and related to intrasinusal septum; the statistical study was carried out with Fisher test with p value <0.05. Surgery was performed on 72 subjects (53 female and 19 male) with a mean age of 44.5 years of age; in 74.7% of patients no complications were observed, while 18.7% presented sinusal membrane rupture. The septum was observed in 18.7% (16 maxillary sinus), showing 12 septum in anterior position and 4 in posterior position; the presence of septum was positively related to membrane rupture (p<0.05). Finally, we can state that the intrasinusal septum was observed in 17% and was related to intraoperatory complications as membrane rupture.29412191222