BACKGROUND: In complex cerebral aneurysms, adequate treatment by complete occlusion is not always possible. Partial occlusion by either proximal or distal occlusion is an alternative. However, the hemodynamic consequences of these partial occlusion options are often not easily predictable. OBJECTIVE: To assess the feasibility of fluid-structure interaction (FSI) analysis to investigate the hemodynamic changes after partial occlusion in cerebral aneurysms. METHODS: Two patients were analyzed. One was treated by proximal occlusion and 1 by distal occlusion. In both, flow replacement bypass surgery was performed. Three-dimensional models were constructed from magnetic resonance angiography (MRA) scans and used for FSI analysis. A comparative study was done for pre- and postoperative conditions. Postoperative thrombosis was modeled and analyzed for the distal occlusion. FSI results were compared to postoperative angiograms and computed tomography (CT)scans. RESULTS: Proximal occlusion resulted in reduction of velocity, wall shear stresses, and disappearance of helical flow patterns in the complete aneurysm. Distal occlusion showed a decrease of velocity and wall shear stress in the dome of the aneurysm. Results were validated against postoperative CT-scans and angiograms at 1-, 7-, and 9-mo follow-up. Addition of thrombus to the distal occlusion model showed no change in velocities and luminal pressure but resulted in decrease in wall tension. CONCLUSION: This pilot study showed hemodynamic changes in 2 patients with proximal and distal occlusion of complex cerebral aneurysms. The FSI results were in line with the follow-up CT scans and angiograms and indicate the potential of FSI as a tool in patient-specific surgical interventions. Copyright © 2017 by the Congress of Neurological Surgeons.