The anatomy of Liliequist's membrane was studied in seven adult human cadavers by a technique that preserves the cisternal shape, stains arachnoid membranes violet, and fills the arteries with red gelatin. Our findings suggest the following about Liliequist's membrane: it is located between the interpeduncular cistern posteriorly, the carotid cisterns anterolaterally, and the chiasmatic cistern anteromedially; it is attached laterally to the mesial surface of the temporal lobe above the tentorial edge; it lies posterior to the infundibulum; and it presents a free edge between the optic tract and the temporal uncus.