The aim of this study is to present a comparison between different mathematical models that can be used to represent renal function, as characterized by the I–hippuran method. Based on physiological considerations, a general model for renal function is established, and three special and less complex models are deriveda prioriby choosing special values for some of the parameters of the general model. The three special models have previously been investigated by other authors. A general‐purpose computer program has been developed to fit any of the four models to the kinetic data. Parameters inherently dependent on the detection technique are calculated by a special method independent of the estimation of the physiologically relevant model parameters. Output from the computer program is used to determine which model gives the most relevant interpretation of I–hippuran renographic curves. In accordance with recent examinations performed by other workers, the results seem to indicate that each kidney can be satisfactorily represented by an ordinary compartment in series with a “delay compartment.”