Odontogenic maxillary sinusitis may occur by draining of an apical dental root abscess into the maxillary sinus. It has been reported that the disease is usually frequent in cases aged of the second and third decades. In most of them, either the first or second molar tooth is assumed to be the origin of the disease. As clinical characteristic symptoms, it is mentioned that an acute unilateral sinusitis appears since the onset and the patient complains a fetid purulent nasal discharge from an early stage. The symptom and its clinical time course in 43 cases with dental maxillary sinusitis, who had been treated by surgical procedures in ENT Clinic in Kitasato University Hospital during past 14 years from 1972 to 1985, were studied retrospectively. The size of the affected maxillary sinus in each case of the disease was measured from the X-ray films. An influence of development of the maxillary sinus to the occurrence of dental sinusitis was discussed by comparing the sizes of the maxillary sinuses in both the group of the disease and the group of simple unilateral maxillary sinusitis.