Foreign bodies in the paranasal sinuses have been occassionally reported. They occur when foreign bodies remain in paranasal sinuses owing to accidents in the construction work of roads, traffic accidents, unvolitional rifle-firing, trying to commit suicide in the psychoneurosis. They also take place by inserting gauze in the paranasal sinus when it is under operation, or by inserting medical tools when it is being treated. When a patient having his teeth pulled out at the dentist's clinic, cotton ball or fragments of teeth can be caused to remain in the paranasal sinus. I experienced the case of a kitchen knife found in the right maxillary sinus long after trauma. The fragment had passed right infraauricular region and remain in right maxillary sinus. I am going to report on the case together with records studies.