The authors report the case of a 26 years old woman who developed four "new" T aneurysms, ten years after the successful clipping of a vertebro-basilar system aneurysm. This observation is discussed in relation to the literature; current views supporting that aneurysms may result from a combination of inherent and acquired tissue weakness associated with hemodynamic effects are cited. Another twelve cases of "de novo" aneurysms developed in patients without previously carotid ligation and reported in the literature are reviewed. Their characteristics in relation to their localisation and their interval time discovery are discussed. The advisibility of repeated angiograms in some patients with aneurysm is discussed as these patients are at an increased risk of hemorrhage from another "new" aneurysm.