The authors present a critical analysis of the various methods of experimental production of aneurysms and report their own method in which saccular aneurysms were produced at the bifurcation of the common carotid artery in dogs with vein patch grafts. The objective point of this study was the creation of an experimental model to evaluate the efficacy of a therapeutic procedure. These aneurysms have a low incidence of thrombosis and a tendency to enlarge and to become spherical. They closely simulate the saccular aneurysms developing spontaneously in the cerebral arteries of man, and as such are useful models for experimental purposes.