Lacunar infarcts are commonly found in the basal ganglia, though little is known about the organization of small-scale microvascular territories that presumably subtend lacunae. We investigated microvascular territories of the lenticulostriate arteries, the recurrent artery of Heubner, the anterior choroidal artery, and striate branches of the anterior cerebral and anterior communicating arteries in perfusion-fixed human brains by simultaneous injection of fluorescent dyes and a radio-opaque substance in 5% gelatin. Territories were defined by ultraviolet illumination of dye and high-resolution mammography of radio-opaque substance. Brains were sectioned coplanar with the Talairach proportional grid system and vascular data were plotted, allowing for application to any human brain. The data suggest first that the lenticulostriate artery, recurrent artery of Heubner, and anterior choroidal artery supply distinct territories of the basal ganglia with minimal overlap and sparse anastomoses between major penetrating vessels. Individual territories are spatially consistent across brains and match the extent of major/minor infarcts. Second, branching patterns of parental, second-, and third-order vessels leading to circumscribed terminal vascular beds could account structurally for "lacunar" infarcts.