The aim of this project was the development of a user-friendly software package for physicians that can be used as an advisor in vessel surgery and as a training tool for medical students. The tool contains a graphical user interface, a mathematical model that describes the relationship of morphology and hydraulics in human arterial networks and an expert system for managing automatic parameter identification and bypass optimization. This system enables physicians to calculate mean flow velocity, mean flow, flow direction and blood pressure at any point of a vessel network. By changing the topology of a network the hydraulic effects of stenoses and bypasses are simulated. The results of these simulation experiments may help physicians in their decisions, whether an operation is necessary and which kind of operation is to prefer.