Cerebral perfusion may be visualized by the dynamic imaging of an intravenously injected bolus (a few milliliters) of clinically approved gadolinium-containing contrast media. During its passage through the vasculature of the brain, the contrast agent induces magnetic field disturbances, which can be seen as signal loss on appropriately weighted dynamic MRI. This article deals with the quantitative analysis of such signal changes, first in terms of tracer concentration and then, via the mathematical approach of deconvolution, in terms of tissue microvascular physiology, culminating in quantitative estimates on a pixel-by-pixel basis of physiologic parameters, such as cerebral blood volume, mean transit time, and cerebral blood flow.