Pressure, red cell velocity, vascular impedance, diameter, hematocrit are continuously recorded in living microvessels (5-75 microns of omentum, skeletal muscle mesentery. Work during the past several has been concerned with the development of methods for obtaining such information and the application of these methods to study systemic and local derrangements of the cardiovascular system. Particular attention is given to the identification of local regulatory mechanisms for both the transport and exchange functions of the microcirculation. The latter has, for the most part, dealt with fluid movements and the determination of filtration coefficients. Also included has been a study of the distribution and properties of the terminal lymphatics. The establishment of these quantitative parameters under steady-state and perturbed conditions has made possible the development of detailed models of microcirculation.