Intracranial saccular aneurysms have been a well known cerebrovascular disease for over fourty years in the Taiwan area and over two centuries around the world. Up to now, information pertinent to the genesis, progression, and thrombosis or rupture of saccular aneurysms has been mainly acquired from autopsies and various in vivo studies. The present review provides relevant hemodynamic information gathered from in vitro studies. The parallel results between in vitro and in vivo or between in vitro and autopsy investigations are also addressed. Emphases are placed on the terminal and lateral saccular aneurysms. The effects of the branches's flow-rate ratio, bifurcation angle, aneurysmal size, parent vessel curvature, and Wormersley number on the intra-aneurysmal flow characteristics are examined in detail, and possible risky factors are identified.