The purpose of this paper is to discuss the treatment required for a patient affected by chronic maxillary sinusitis following a sinus grafting procedure with an alloplastic material. Sinusitis was not the consequence of migration of alloplastic material into the maxillary sinus, but rather the consequence of overfilling the subantral space followed by obstruction of the ostium. The treatment involved removal of the alloplastic material and correction of the ostium obstruction via a nasal endoscopic approach.