After the early surgery for ruptured intracranial aneurysms, small infarcts developed in the head of caudate nucleus and nearby structures. In the present report, the mechanism of infarction was studied and problems of operative techniques were pointed out.Pterional approach was employed in 90 0f 112 patients with aneurysms on the anterior circulation for neck clipping performed within 72 hours after ruptures. Seven of them developed small infarcts in the head of caudate nucleus and surrounding region, which are perfused by Heubner's artery. Five of seven cases were with anterior communicating artery aneurysm, the rest with middle cerbral artery aneurysm. Temporary clipping less than 5 minutes was employed in 3 cases. No premature rupture of hypotensive episode was noted during operations. Courses of 26 Heubner's arteries were analized in 13 cadaveric brains. Ten of 26 Heubner's arteries (38%) run anteriorly, not superiorly to A1portions, making curved courses in the inferior surface of frontal lobes with their convexities anteriorly. Seven of 26 Heubner's arteries (27%) give rise to perforating branches near the olfactory stem in the inferior surface of frontal lobes. Retraction of frontal lobe in pterional approach can obviously cause traction and/or kinking of the origin of Heubner's artery, or compression of its perforating site, any of which leads to the circuratory impairment. Kinking or compression of Heubner's artery caused by its retraction can cause serious brain damage just after subarachnoid hemorrhage, when cerebrovascular autoregulation is lost and cerebral metabolism is impaired.When the frontal lobe is retracted in pterional approach, Heubner's artery should be freed from surrounding structures and be handled in such a manner as not to cause its compression and/or kinking.