Objectives: With rapid advances in endoscopic neurosurgery, it has become possible to treat some lesions located in the anterior skull base through a transnasal approach. This anatomic study was undertaken to describe the area of surgical exposure of the anterior skull base afforded by transnasal approaches with an endoscope, as well as to provide references for clinical practice. Methods: Thirty bony skull base specimens (all Chinese) were used, and 10 injected adult cadaver heads (all Chinese) were dissected for a simulated endoscopic transnasal approach to the anterior skull base. The distance between the bilateral optic canals was measured in skull base specimens and the distance between the columella and anterior ethmoid artery or posterior ethmoid artery was measured on both sides in adult cadaver heads. Results: The optic canals were 15.13 +/- 1.69 mm apart. The distance between the columella and posterior ethmoid artery was 71.01 +/- 3.99 mm on the left side and 72.27 +/- 3.97 mm on the right side. The distance between the columella and anterior ethmoid artery was 64.811 +/- 3.74 mm on the left side and 64.18 +/- 3.74 mm on the right side. The endoscopic transnasal approach to the anterior skull base exposed the optic protuberance, sellar floor, crista galli, anterior ethmoid artery, and posterior ethmoid artery. In addition, bilateral olfactory bulbs, olfactory tracts, and optic nerves beneath the dura mater were also revealed. Conclusions: The anatomic data as well as established anatomic landmarks associated with endoscopic surgery would benefit clinical practice. (C) 2010 Elsevier B.V. All rights reserved.