The aim was to assess the physiological meaning of the parameters of three different windkessel-derived models of left ventricular load (J Appl Physiol 103: 66–79, 2007). These models are denominated W4P, W4S and IVW. The W4P and W4S configurations are derived from the three-element windkessel by connecting an inductance, L, in parallel or in series, respectively, with aortic characteristic impedance, R_c. In the IVW model, L is connected in series at the input of a viscoelastic windkessel, where a Voigt cell (a resistor, R_d, in series with a capacitor, C) accounts for arterial viscoelasticity. All three models were applied to the ascending aortic pressure and flow measured in a ferret of 1.5 kg BW. After parameter estimation was accomplished by fitting model predicted pressure to experimental pressure, generalized sensitivity functions (GSFs) were generated (Ann Biomed Eng 27: 607–616, 1999) to test the physiological consistency of each model parameter. Superimposition of L-related GSFs to the flow pulse wave yielded the conclusion that the L-term of both W4S and IVW models can be given the meaning of arterial inertance, while this meaning is inconsistent with the role the L-term plays in the W4P. Superimposition of both R_c-related and R_d-related GSFs to arterial pressure and volume waveforms indicated that the R_c is inconsistent with the meaning of aortic characteristic impedance, while the IVW-based viscoelastic arterial representation has physiological relevance.