• The use of systems analysis as an experimental tool for solving complex physiological problems is not new. Actually, systems analysis is merely the logical analysis of how systems perform. However, modern usage of the term implies a more formalized type of logic, especially a type of logic that includes quantification at each step in the analysis. Several of the figures in this paper illustrate systems analysis flow diagrams that show interrelationships between the different parts of simple or complex mechanisms for the control of arterial blood pressure. One can readily see that each part of each systems analysis diagram is only a symbolic way in which a composite of individual physiological phenomena fit together in a complete system.The principal advantage of the formalized systems analysis approach to understanding any physiological mechanism is that it often allows greater depth of thought than our minds can perform using simple logical procedures. The mind has the capability of holding and analyzing perhaps five to ten different sequential phenomena, each occurring at different rates and each interrelated with the other phenomena by various cross-linkages. However, beyond this size of system it is almost impossible to think through all the complex relationships simultaneously. On the other hand, the modern computer can handle literally thousands of such crosslinking interrelationships at the same time and can develop answers that the mind alone cannot achieve. Now setting aside this philosophizing about systems analysis per se, we will attempt to show how the systems analysis approach has been useful in the study of long-range arterial blood pressure control and the understanding of hypertensive