In this paper, a case of ruptured newly-developed right internal carotid posterior communicating artery bifurcation aneurysm, which occurred 11 years after contralateral common carotid artery ligation for a ruptured left side aneurysm, is reported.Common carotid artery ligation for the left internal carotid posterior communicating artery bifurcation aneurysm seemed to be effective to some extent from the following view points: rebleeding from the ipsilateral aneurysm was prevented and a decrease in size of that aneurysm was obtained.The new aneurysm might have developed due to the long-term hemodynamic stress exerted on the pre-existing fragility of the arterial wall. Such stress may have resulted from increased blood volume in the ipsilateral internal carotid artery after the contralateral common carotid artery ligation.
