It is the function of the vascular system, through a complex network of arteries, capillaries and veins, to maintain cellular homeostasis. As research scientists it is necessary to understand not only some of the basic properties of the blood vessel itself but also how these vessels differ in cellular and physiological function. This review provides an overview of the basic physiological and pharmacological tenets of blood vessels. It also briefly describes in vivo and in vitro methods used in the measurement of blood flow and blood vessel function. It is hoped that this review will provide readers of this focussed issue of the Journal of Pharmacological & Toxicological Methods with an appreciation of the many mechanical, electrical and biochemical methodologies described within this issue.