Cineangiograms of 20 patients were analyzed with a computer to calculate instantaneous left ventricular volume and the rate of volume change (dV/dt, flow) for a cardiac cycle. Patients were divided into four groups : group I-normal, group II-mitral stenosis, group III-left ventricular volume overload, and group IV-coronary artery disease. The instantaneous flow (ordinate) -volume (abscissa) relationship showed a loop which rotated in a counterclockwise direction accompanied by rapid downslopes during early diastole in groups I and III. The steepness of the early diastolic downslope was markedly decreased in groups II and IV. In order to evaluate the findings numerically, flow at the early 20% of diastolic volume change (F₂₀), F₂₀ corrected with peak diastolic flow (F₂₀/F_d) and F₂₀ corrected with peak systolic flow (F₂₀/F_s) were measured. F₂₀/F_s and F₂₀/F_d were significantly lower in groups II and IV than in groups I and III. On the other hand, stiffness constant obtained during later diastole stayed within normal limits in groups I and II, but the index was increased in groups III and IV. Possible mechanism for the decreased flow during early diastole, i.e., delayed relaxation during early diastole in groups II and IV, and dissociation between early diastolic relaxation and the stiffness constant obtained during later diastole in groups II and III are discussed.