Abstract
The general mathematical theory of measurement of blood flow by dye dilution techniques is discussed. The mathematical procedure for handling the recirculation problem is described, and it is shown that, in general, sampling of concentration at a single point is not sufficient to uniquely determine both the volume and flow in a vascular bed. The more basic problem of synthesizing a mathematical model of the circulation is analyzed. A general probabilistic scheme for handling transport problems of this kind is outlined, and results obtained for exchange of labeled material between the vascular and extravascular fluid compartment are described.