Thirty eight consecutive cases of intracranial arterial aneurysms collected during the last decade in the same department of neurology are reported, the aneurysms being revealed by a non hemorrhhagic semeiology, i.e. without clinical meningeal syndrome. In 31 cases, the aneurysm seemed to be related to the clinical manifestation: in 14 cases, it was an acute headache, characterized by its suddenness, immediate maximum intensity, spontaneous and fastly regressive course. It occurred without any symptoms (6 cases) or associated with an epileptic seizure (1 case), or an ophthalmoplegia (7 cases). The course was often relapsing. In 8 cases, it was a cerebrovascular accident of ischemic type; in 6 cases, a pseudo-tumoral syndrome; in 2 cases, an epilepsy; in 1 case, a migraine. For the further 7 cases, the aneurysm was diagnosed fortuitously when investigating a non related disease. The present series shows: the high incidence of the non hemorrhagic forms of aneurysms since they account for 40 p. 100 of the aneurysms cases detected during the same period in our neurological department. The various clinical manifestations are already well-known, mainly the acute headache and the pseudo-tumoral forms. The aneurysm-related cerebrovascular accidents seem to be relatively frequent; 2 cases of the present series give the opportunity for a discussion about the relations between a spontaneous thrombosis and a definitive anatomical cure of the aneurysm. Finally, other cases lead to suspect aneurysms as a possible cause of epilepsy or of migraine. The prognosis of these non hemorragic forms of aneurysms is much better than that of ruptured aneurysms. The direct intracranial surgical cure of the lesion gives on the whole excellent results. Such a treatment must be advocated whenever possible for any unruptured symptomatic aneurysm, as the risk of their rupture or clinical relapse is far from being negligible. The strategy is more difficult to define for asymptomatic unruptured aneurysms as the actual risk of subsequent rupture or other clinical manifestations is not sufficiently known.