Detailed numerical simulations of blood flow in arteries with various malformations and its conjugate loads on the vessel walls have been a research topic for specialized medical and engineering communities over decades. The present state of computing resources and software allows access to these elaborate diagnostic and research tools to a broad user circle and even to integrate them into clinical workflows. To tap the full potential of hemodynamic simulations, a Grid-based “virtual vessel surgery” application has been developed and deployed as part of the image processing module of the MediGRID project of the German Federal Ministry of Education and Science (BMBF). The very resource-intensive parts of that application, including not only the numerical simulation itself, but also automated data pre- and post-processing and visualization are implemented and are made available through the MediGRID portal. Some highly interactive workflow steps of the application are left at the user site but automated – via a specially developed Web interface – to a degree allowing intuitive, fast interaction and seamless integration with the Grid components. Standard middleware provided by D-Grid is used throughout. The complete workflow is implemented into the grid and can in principle be carried out using no external software. It was applied to real vessel data with a stenosis and an aneurysm, respectively.