Serial recording of systolic time intervals (STI) was used to assess changes in left ventricular (LV) function in 92 patients with stable angina undergoing coronary angiography and LV cineangiography. On the basis of angiography, patients were placed in the following study groups: mild or absent coronary artery disease group -21 patients with less than 70 per cent occlusion of all coronary arteries, considered to have non-significant coronary artery disease and not needing bypass surgery; surgical bypass group-52 patients with evidence of significant (less than 70%) obstruction of at least one coronary artery who underwent myocardial revascularization; and medical group-19 patients with evidence of significant coronary artery disease not undergoing bypass surgery. Measured STI, corrected for heart rate and sex, were expressed as indices. No significant differences were noted in the mean STI from the time of initial evaluation to second evaluation 3 to 6 months later in either the mold or absent coronary artery disease patients or the medical group. In the surgical bypass group, however, serial studies at initial angiographic evaulation and 3 to 6 months after bypass surgery showed a shortened pre-ejection period (PEP) from 150 +/- 20 to 142 +/- 16 mn (P less than 0-001), prolonged left ventricular ejection time (LVET) from 396 +/- 21 to 409 +/- 14 ms (P less than 0-02), and decreased PEP/LVET from 0-45 +/- 0-11 to 0-04 +/- 0-07 (P less than 0-02). Paired data analysis of the three groups also showed a significant change only within the surgical bypass group from initial to find study, with a shortened PEP (P less than 0-002), prolonged LVET (P less than 0-001), and decreased PEP/LVET (P less than 0-001). These data suggest improvement in LV function in patients with significant coronary artery disease within a few months of myocardial revascularization, without demonstrable change in STI in those patients with coronary artery disease not subjected to revascularization.