A method is disclosed for forecasting the contrast medium flow in a living body, in particular in a patient, in which a defined test bolus with a contrast medium is injected, preferably intravenously and with a known injection flow profile, into the body, preferably into a blood vessel. The time concentration profile of the contrast medium is observed and determined over a limited time period with a number of measuring instants at at least one location in the body with the aid of a tomographic method. The time profile of the contrast medium concentration of another contrast medium dose is forecast with the aid of a linear cause/effect formulation from the measured data obtained via the distribution of the contrast medium. The following calculation formula is then used for forecasting the time concentration profile {tilde over (c)}.sub.R(t) of the contrast medium at at least one of the previously measured locations of the body:.function..times..times..intg..times.d'.times..function..time- s..times..times..DELTA.'.times.'.function.' ##EQU00001##