The anterior choroidal artery blood supply territory was studied in 100 adult human cerebral hemispheres, of which 50 came from whites (40 men and 10 women) and 50 from negroes (31 men and 19 women). Age was not taken into consideration. The brains, secured at the necropsy table were injected with coloured mass and, after fixation in 10% formalin, each hemisphere was dissected in order to expose the whole anterior choroidal artery trunk, from its origin, backwards to the choroid plexus of the lateral ventricle. Each hemisphere was then free-hand sectioned horizontally, slices 0.5 cm thick, to permit observation of the deep territories which were injected by the contrast. It could be demonstrated that the anterior choroidal artery arises always from the internal carotid artery and that its blood supply territories are the following: uncus, hippocampus, optic tract, choroid plexus of the inferior horn of the lateral ventricle and posterior limb of the internal capsule (100%); tail of the caudate nucleus (99% ± 0.99); intermediate 3/5 of the cranial portion of the cerebral peduncle base, amygdaloid nucleus and zona incerta (98% ± 1.40); lateral 1/5 of the cranial portion of the cerebral peduncle base (92% ± 2.71); anterior part of the lateral geniculate body (89% ± 3.13); medial segment of the globus pallidus (88% ± 3.25); subthalamic nucleus (39% ± 4.88); lateral nuclear group of the thalamus (26% ± 4.39); lateral segment of the globus pallidus (17% ±3.76); posterior nuclear group of the thalamus (13% ± 3.36); posterior part of the putamen (9% ± 2.86); medial 1/5 of the cranial portion of the cerebral peduncle base (7% ± 2.55) and substantia nigra (3% ± 1.71) No significant racial and sexual differences were found.