The main objective of the stereological approach is to make estimations of parameters of geometrical structures using sampled information. The nature of the structure under study in itself does not matter. it may include any macro or microstructure in biology, materials sciences or indeed geology. This approach allows inference of geometrical parameters such as volume, surface area, number, thickness and spacing. In the stereological approach, the exact nature or function of the structure is not important. Holes can also be considered as structures. The wide applicability of this approach is because it relies on basic facts of geometry and statistics. In Biology, it provides a spatial framework upon which to lay physiological and molecular information. Stereology has been applied to a wide variety of problems in Biology in fields such as Neurobiology, Reproductive Biology and Cancer Cell Biology. In this presentation, the application of this approach to a variety of vascular beds will be illustrated with examples including the nervous system (brain and spinal cord) and the reproductive system (endometrium). The stereological approach can provide access to the three-dimensional spatial framework of complex vascular beds. The aim of this paper is to highlight the usefulness of this approach to the study of the vasculature. (c) 2007 Elsevier Inc. All rights reserved.