An understanding of the age-related changes in the volume of the normal maxillary sinus will help to identify sinus abnormalities. Normal maxillary sinus volume was measured on axial CT scans in 115 cases, and analysed in relation to age, the presence of premolar and molar teeth, size of the midfacial skeleton and body height and weight. The volume ranged from 4.56-35.21 cm3 (mean: 14.71 +/- s.d. 6.33 cm3) in patients aged over 20 years. There was no significant sex difference and a close correlation between the two sides was found. The volume increased up to the age of 20 years, but then decreased. There was no significant difference in patients with and without maxillary premolars and molars between the ages of 50 and 79 years. The difference in right and left dentitions had no influence on the maxillary sinus volume over the age of 20 years. Adult maxillary sinus volume correlated with the interzygomatic buttress distance. In adult females, there was a significant correlation between the volume and the zygomatic-occipital distance. In adult males, the volume correlated with body height and weight. It appears that volume changes with age might be related to skeletal size and physique.