A new model for simulation of recirculation has been developed which describes the measured concentration-time course of a drug in the aorta. It is based on repetitive convolution of the injected input dilution curve with a body transport function plus the input dilution curve. If the basic shape of a body transport function, i.e. such as log-normal distribution, is known, it is possible to calculate the parameters of this function with a non-linear least-squares procedure from measured tracer dilution data. In the present investigation this algorithm is used to estimate the body transport function for experimental data, obtained in two experiments with sheep. Once the body transport function is known, the formula can be used to describe the dispersion of a drug. Intravascular concentration time curves at different places in the body can also be predicted or the blood volume can be estimated.