In order to assess the possible importance of regional non-uniformity of left ventricular function, angiograms of 42 normal subjects and 105 patients with coronary artery disease were digitised frame by frame. Regional curvature around the cavity was assessed, only positive curvature being compatible with ellipsoidal geometry. In normal subjects, positive curvature of the anterior wall was shown by all, but on the inferior wall was present in only 12 (28%) at end-diastole and five (12%) at end-systole. In patients with ischaemic heart disease, anterior wall curvature was again positive in all but four with apical aneurysm, but positive curvature of the inferior wall was present more frequently than normal, 47 (42%) at end-diastole and 39 (36%) at end-systole. In these patients, positive curvature at end-diastole was associated with reduced wall movement during ejection. Though the pattern of coronary artery involvement was random, there were conspicuous regional differences in the distribution of abnormal wall movement during isovolumic relaxation. Outward movement was found only on the anterior wall. Abnormal inward movement was five times as frequent on the inferior wall as on the anterior. An ellipsoidal cavity outline is not therefore characteristic of the normal left ventricle and, when present, this configuration is likely to be associated with a reduced amplitude of inferior wall movement. Regional differences of both structure and function can thus be shown in normal and abnormal hearts. They may arise from variation in local fibre architecture. Their presence must be taken into account in interpreting abnormalities of left ventricular function.