During osteoplastic surgery of the maxillary sinus the surgical defect in the lateral wall of the maxillary sinus is re-closed by means of free reimplantation of the "bone lid", which had been temporarily removed together with the integral mucosa, during creation of the access. This "bone lid"-method has so far been employed successfully in approx. 600 cases. For covering the basal area of the bone lesion of the drainage window to the lower nasal passage, created during surgery by means of a flap of mucosa and periosteum, a novel type of tamponade using an inflatable balloon was tested. The following pages report on the surgical techniques employed and on systematic follow-up investigations.