The authors analyse 14 cases of aneurysm occurring at the point of bifurcation of the internal carotid artery into the middle and anterior cerebral arteries. Distinguishing features of this aneurysm are often its fairly large size and extensive implantation on the artery. Clinical symptoms are not specific but various neurological signs are frequent. The bifurcation of the carotid artery is not always readily visible; oblique views and angiotomography are often necessary. Owing to the usual severity of the natural evolution of this type of aneurysm (death in six out of eight cases), surgical treatment is advisable. Ligation of the carotid artery is disadvised because of the unpredictable nature of its results (further fatal haemorrhage in one out of three cases).