Saccular cerebral aneurysms were successfully induced in rats treated with beta-aminopropionitrile, deoxycorticosterone and salt hypertension and ligation of unilateral common carotid artery. This experiment was performed on the hypothesis that if hemodynamic stresses were increased on the fragile, cerebral arterial wall of beta-aminopropionitrile-fed animals, cerebral aneurysms might be produced. Although the incidence of cerebral aneurysms was low and the contributory mechanisms of these procedures must be more clearly elucidated, the present results show that saccular cerebral aneurysms are really inducible in experimental animals.