A study of 24 adult Caucasian cadavers was undertaken to assess and document the anatomical measurements within the nasal cavity and sphenoid sinus as routes of instrumentation utilized in sublabial transsphenoidal and endonasal endoscopic approaches. Five measurements were performed. The mean thickness of the anterior sellar wall was 0.8 +/- 0.3 mm for both the sellar and presellar types of sinuses, respectively. Also, the mean thickness of the bony floor of the sellar type of sinus was 0.9 +/- 0.4 mm. In addition, the mean depth of the sphenoid sinus was 13.6 +/- 5.1 mm for the sellar type and 13.2 +/- 3.9 mm for the presellar type of sinus. Furthermore, the mean distance between the suspinale (inferior-posterior edge of the anterior nasal spine) and the anterior sphenoid wall was 62.3 +/- 4.6 mm for the sellar type of sinus (P < 0.05) and 60.6 +/- 2.9 mm for the presellar type of sinus, while the distance between the subspinale and the anterior sellar wall had a mean value of 75.9 +/- 6.3 mm for the sellar type of sinus (P < 0.05) and 73.8 +/- 4.2 mm for the presellar type of sinus, with the distance of the sellar type sinus being greater for male specimens. Sphenoid sinus pneumatization was of a conchal type in 4%, presellar type in 28%, and sellar type in 68% of subjects examined. The results of the current study expand upon current anatomical knowledge and may be beneficial in the future refinement of surgical instrument design.