Clinical trials indicate that an intracranial aneurysm is most likely to rupture on the dome area where the wall is weak (1-3). Even though several factors contribute, the cause for rupture is still unclear; hemodynamic forces are believed to significantly effect the growth, development and rupture of an aneurysm. The entrance length or the ostium width, the shape and size of the aneurysm, the Reynolds number of the flow and the shape of the parent artery, all can contribute toward the rupture of an aneurysm (4, 7). A neck area, if present, can substantially influence the flow into the aneurysmal volume resulting in higher hemodynamic forces on the aneurysmal wall. The objective of this study is to investigate the effects of hemodynamic forces for suggesting vulnerable regions or points of rupture of an aneurysm considering the shape and size of the aneurysm, its ostium width and the Reynolds number (Re) of the flow. The research was done in two parts — theoretical computations with a CFD software Fluent were performed on 2D models of aneurysms and experimental determinations of the in-vitro velocity vector field with 2-D particle image velocimetry (PIV) were made with glass models of aneurysms.