A variable, e(t)=p(t)/v(t), is proposed for formulating the ventricular pumping of blood, as a concept of the reciprocal of ventricular compliance, where t=time, p(t)=time course of the intraventricular pressure and v(t)=that of the intraventricular volume. For actual computation, e(t)=p(t)/{v(o)-∫^t_oi(t)dt} where v(o)=v(t) at t=o or enddiastolic volume and i(t)=aortic blood flow. v(o)=(1-ρ)^-1•v_s, where ρ=residual volume ratio measured by a thermodilution method and v_s=stroke volume or integral of i(t) in the cardiac cycle. e(t) is calculated of areflexive left ventricles of dogs under various v(o) controlled by occlusion of the vena cava. In spite of conspicuous changes of p(t), i(t) and v(t), e(t) has ap-proximately unchanged time course and magnitude in a wide range of v(o). A model of ventricular pumping is presented with e(t).