Diastolic suction (DS) can be defined as that property of the ventricle by means of which it tends to refill itself during early diastole, independent of any force from the atrium. Although thought to be significant in the left ventricle (LV), right ventricular (RV) DS has received little attention, probably because of RV geometry. Our recent LV studies have shown that DS is related to both decreased elastance (i.e.,, the relaxation time constant) and end-systolic volume (V_LVES), thus reconciling the two mechanisms that have been used to explain the concept of DS. We hypothesized that RV DS would similarly depend on and V_RVES. In 6 anesthetized open-chest dogs, aortic, RV, right atrial (RA), pulmonary arterial (PA), RV pericardial pressure, tricuspid velocity and PA flow were measured. V_RVES was calculated by measuring distances between 8 ultrasonic crystals. and V_RVES were manipulated by volume loading/caval constriction and isoproterenol/esmolol. We calculated the total energy (I_W-) of the backward expansion wave generated during RV relaxation and that component causing DS (I_W-(DS)); i.e., the energy remaining after tricuspid valve opening). I_W- (I_W-(DS)) also was found to be inversely related to and to V_RVES [i.e., I_W- = -8.85 e^(-0.0423) e^{[-0.0665(%V_RVES)]}]. Thus, as for the LV, the energy of the backward-going wave generated by the RV during relaxation depends both on the rate at which elastance decreases and on the completeness of ejection. Despite the RV's thin wall and non-spherical shape, DS appears to be an important mechanism.