Sinus lift is a necessary procedure when patients do not have a sufficient quantity of bone tissue height or thickness for the placement of dental implants in the posterior maxilla. The procedure has a high percentage of success, but it presents a number of complications. The most frequent complication is the membrane perforation, especially in the presence of a maxillary sinus with septa. Therefore, it is important to understand the anatomy and handling of sinus septa. If a perforation exists, we can choose to repair the membrane and to proceed with the intervention, or to abandon the procedure, depending on the size of a perforation. However, it is a negative factor for survival rate when implants are placed in sinus lifts with perforated membrane. (J. Family Dent. 6(4): 17-26, 2012)