The anterior perforating arteries, the group of arteries that enter the brain through the anterior perforated substance (APS), were examined using X 3 to X 40 magnification in 50 cerebral hemispheres obtained from 25 adult cadavers. These arteries arose from the internal carotid, middle and anterior cerebral, and the anterior choroidal arteries. The carotid branches to the APS arose distal to the origin of the anterior choroidal artery. The anterior choroidal artery branches arose from the main or superior branch of the artery. The middle cerebral artery branches to the APS (the lenticulostriate arteries) arose from the M1 and M2 segments and were divided into medial, intermediate, and lateral groups, each of which had a characteristic configuration. The anterior cerebral artery branches arose from the A1 segment and from the recurrent artery. The internal carotid and anterior choroidal artery branches entered the posterior half of the central portion of the APS. The lenticulostriate branches entered the middle and posterior portions of the lateral half of the APS. The A1 segment gave rise to branches which entered the medial half of the APS above the optic nerve and chiasm. The recurrent artery sent branches into the anterior two-thirds of the full mediolateral extent of the APS. The relationship of these branches to the cerebral structures above the APS and to the common aneurysm sites is reviewed.