The total stroke volume of the left ventricle (LV) is equal to the sum of the regional cavity shrinkage. Since nonuniformity of regional wall motion in LV has been well documented even in normal subjects, the extent of the contribution of each region to total stroke volume cannot be easily determined. To assess the left ventricular regional contributions to total stroke volume under normal conditions and in compensated chronic mitral or aortic regurgitation, LV cineangiograms were analyzed in 14 normal subjects (N), 8 patients with mitral regurgitation (MR) and 10 patients with aortic regurgitation (AR). We assumed that the LV cavity could be viewed as a stack of 30 half-cylindrical discs, 15 in the anterior and 15 in the inferior wall regions. LV chamber shape was more spherical in MR than in N, but was more conical in AR. Percent regional hemichordal shortening was significantly decreased in the anterobasal and anteroapical walls in AR, but was similar between N and MR. The regional contribution to total stroke volume showed a significant quadratic correlation with the end-diastolic regional shape index (N, r = 0.87; MR, r = 0.79; AR, r = 0.90), which was defined as the regional hemiaxial length divided by the LV long-axis length, but was not correlated with percent regional hemichordal shortening. Therefore, stroke volume is generated mainly in the mid-ventricular portion in N and MR, but in the basal portion in AR due to the characteristic change in cavity shape.