Origin, course and ramification of the "A. laminae tecti" (quadrigeminal artery) and the Rr. thalamogeniculati were examined on 115 Hemispheres by microdissections. The A. lamina tecti arises from the posterior cerebral artery in the area between 12 mm proximal and 10 mm distal of the junction with the posterior communicating artery. This vessel is doubled in 18% and has an outer diameter from 0.37 mm (Mean). It leaves Rr. interpedunculares, pedunculares and R. colliculi craniales which origins, number, courses and anastomoses were determined. The R. thalamogeniculati were estimated in similar manner.