Abstract
Clip compression injury of oculomotor nerve (ON) is a preventable complication of aneurysm microsurgery. The author illustrates this condition in which ON was inadvertently occluded by the clip during repairing posterior communicating artery (PcoA) aneurysm. The report indicates that the surgeon should be meticulous in identifying and protecting ON at clipping stage when PcoA aneurysm prematurely bursts.