In comparison to arterial hemodynamics, there has been relatively little study of venous hemodynamics. We propose that the venous system behaves just like the arterial system - waves propagate on a time-varying reservoir, the Windkessel, which functions as the reverse of the arterial Windkessel. During later diastole, pressure increases exponentially to approach an asymptotic value as inflow continues in the absence of outflow. Our study in 8 open-chest dogs showed that the Windkessel-related arterial resistance was ~62% of the total systemic vascular resistance while the Windkessel-related venous resistance was only ~7%. Total venous compliance was found to be 21 times larger than arterial compliance (n=3). Inferior vena caval (IVC) compliance, C_IVC (0.32 ± 0.015 (SEM) ml/mmHg/kg), was ~14 times the aortic compliance, C_a (0.023 ± 0.002 ml/mmHg/kg) (n=8). Despite greater venous compliance, the variation of venous Windkessel volume (i.e., compliance times Windkessel pulse pressure), V_Wk-IVC (7.8 ± 1.1 ml), is only ~32% of the variation in the aortic Windkessel volume, V_Wk-a (24.3 ± 2.9 ml), because of the larger arterial pressure variation. In addition and contrary to previous understanding, waves generated by the right heart propagated upstream as far as the femoral vein but the excellent proportionality between the excess pressure (i.e., P_IVC-P_Wk-IVC) and venous outflow (Q_IVC) suggests that no reflected waves returned to the RA. Thus, the venous Windkessel model not only successfully accounts for the variations in the venous pressure and flow waveforms but also, in combination with the arterial Windkessel, provides a coherent view of the systemic circulation.