The Vascular Modeling Toolkit is a collection of libraries and tools for 3D reconstruction, geometric analysis, mesh generation and surface data analysis for image-based modeling of blood vessels. VMTK can be used via its standalone interface, included as a Python or C++ library, or as an extension to the medical image processing platform 3D Slicer. By providing multiple user interfaces with various requirments of technical ability, VMTK aims to be usable by anyone with an interest in medical image processing; be they clinicians, researchers, industries, or educational institutions.