Arterial aneurysms continue to provide a clinical challenge for neurosurgeons and vascular surgeons. Many different animal models have been developed in which the pathogenesis, growth, rupture and treatment of these aneurysms can be investigated. These animal models have been reviewed here, with the focus on saccular aneurysms in the muscular cerebral arteries and fusiform aneurysms in the elastic aorta. Consideration of the animal models described indicates appropriate experimental models and new directions for the development of improved models in which to test the effects of pharmacologic factors in limiting the growth and rupture of aneurysms.