Coronary heart diseases are the major cause of deaths in the United States as well as in most other countries. Approximately 16.7 million people die from heart diseases every year according to estimates of the World Health Organization (WHO). Recent studies show that common methods of treatment, such as bypass surgery, do not necessarily help to avoid coronary heart disease. Consequently, there is a need for a better understanding of the functionality of the heart. Here, virtual models depicting structure and/or operation of the heart can help. In the same way, visualization is required to aid in the analysis of these virtual models. In this paper, a method for generating a virtual geometric model of a vascular tree is described. The necessary data is either based on CT scans or on a simulation using statistical methods. The software allows to explore the geometric model interactively from an external view point, where different analysis options are available. Several examples are given to prove the usefulness of the visualization system and to demonstrate how it helps scientists to quantitatively analyze their models.