This review describes the theories of transport of solutes and solvent across the endothelial membrane of continuous capillaries which constitutes the microvascular exchange domain in peripheral tissues such as the heart, skeletal muscle, adipose tissue, and skin. The theories of equivalent endothelial pores and fiber matrix are considered together with discussions of the various methodological techniques for measurement of fluxes and flows, and the results and implications of anatomical and physiological examinations are considered.