Hemodynamic　parameters　play　an　important　role　in　aneurysm　formation　and　growth.　However,　it　is　difficult　to　directly　observe　a　rapidly　growing　de　novo　aneurysm　in　a　patient.　To　investigate　possible　associations　between　hemodynamic　parameters　and　the　formation　and　growth　of　intracranial　aneurysms,　the　present　study　constructed　a　computational　model　of　a　case　with　an　internal　carotid　artery　aneurysm　and　an　anterior　communicating　artery　aneurysm,　based　on　the　CT　angiography　findings　of　a　patient.　To　simulate　the　formation　of　the　anterior　communicating　artery　aneurysm　and　the　growth　of　the　internal　carotid　artery　aneurysm,　we　then　constructed　a　model　that　virtually　removed　the　anterior　communicating　artery　aneurysm,　and　a　further　two　models　that　also　progressively　decreased　the　size　of　the　internal　carotid　artery　aneurysm.　Computational　simulations　of　the　fluid　dynamics　of　the　four　models　were　performed　under　pulsatile　flow　conditions,　and　wall　shear　stress　was　compared　among　the　different　models.　In　the　three　aneurysm　growth　models,　increasing　size　of　the　aneurysm　was　associated　with　an　increased　area　of　low　wall　shear　stress,　a　significant　decrease　in　wall　shear　stress　at　the　dome　of　the　aneurysm,　and　a　significant　change　in　the　wall　shear　stress　of　the　parent　artery.　The　wall　shear　stress　of　the　anterior　communicating　artery　remained　low,　and　was　significantly　lower　than　the　wall　shear　stress　at　the　bifurcation　of　the　internal　carotid　artery　or　the　bifurcation　of　the　middle　cerebral　artery.　After　formation　of　the　anterior　communicating　artery　aneurysm,　the　wall　shear　stress　at　the　dome　of　the　internal　carotid　artery　aneurysm　increased　significantly,　and　the　wall　shear　stress　in　the　upstream　arteries　also　changed　significantly.　These　findings　indicate　that　low　wall　shear　stress　may　be　associated　with　the　initiation　and　growth　of　aneurysms,　and　that　aneurysm　formation　and　growth　may　influence　hemodynamic　parameters　in　the　local　and　adjacent　arteries.