Externally recorded STI were compared with invasively determined EF in 10 normal subjects and 86 patients with various forms of chronic heart disease. From phono-, apex-, and electrocardiograms and carotid pulse tracings, recorded without rigidly controlled conditions (postabsorptive state, fixed time of day, exclusion of atrial fibrillation, and discontinuation of cardiac drugs), PEP, electromechanical interval, isovolumic contraction period, and LVET were measured and deltaPEP (deviation from predicted normal) and PEP/LVET were drived. EF was determined with biplane angiocardiographic methods. Patients were divided into groups based on pathophysiology and state of clinical compensation. The ability of STI to discriminate abnormal from normal function, as compared with EF, varied with each noninvasive parameter and with each physiologic group. On a group basis, the discriminatory ability of PEP was better than that of other noninvasive parameters studied, but did not always parallel that of EF. PEP also tended to correlate better with EF than the other noninvasive measurements. On an individual patient basis, however, the ability of even PEP to predict EF was poor. It is concluded that the usefulness of assessing left ventricle function in chronic heart disease by STI is limited.