An identification scheme is developed for the determination of several parameters of a modified "Windkessel" model of the systemic arterial system for an individual patient undergoing cardiac catheterization. The scheme utilizes a modification of the well-known Prony method [10,11] as a "starter method" to determine good nominal values for the model parameters being varied. These values then serve as input to an iterative nonlinear least squares identification method (Marquardt method [14]) which then converges to final values of the parameters. Solution of the model equations with these parameter values yields the best fit of model generated and observed aortic and brachial artery pressures. This technique, coupled with a method for determining the mechanics of the left ventricle (e.g., the elastance concept [1-5]), permits the functional characterization of the hemodynamic properties of the left ventricle and its systemic load for an individual patient.