RESUMO
Objective. To determine the variability of the position of the ostia of the sphenoid sinus. Method. Thirty two dry skulls were examined under X6 magnification. The septae and nasal conchae were removed in order to expose the anterior wall of the sphenoid sinus. A caliper was used for measurements.Results. We found two ostia in each skull, except in one case (the left ostium was absent). In just four skulls the inferior edges of both ostia were found in the same height. In just one skull the superior edges of both ostia were found in the same height. The distance from the internal edge of the right ostium to midline is, on average, 2.04 mm (from 0.3 to 5.3 mm). The distance from the internal edge of the left ostium to midline is, on average, 2.18 mm (from 0.2 to 5.1 mm). Conclusion. A great variability exists of the position of the ostia of the sphenoid sinus. This knowledge is useful when a transsphenoidal surgery is carried out.