It is generally recognized that conventional hemodynamic measures are not consistently altered by digitalis in patients with congestive heart failure. In normal subjects. digitalis has been found to abbreviate the systolic time intervals at a time when other hemodynamic changes are minimal. The present studies were designed to study the response in systolic time intervals among patients with heart failure and to test whether their determination may offer a more consistent measure of the response to digitalis than other hemodynamic parameters. Thirteen patients with clinically conspicuous congestive heart failure due to arteriosclerotic (5), hypertensive (5) and primary myocardial disease (3) were studied before and 55 to 65 minutes after cedilanid-D (1.2–1.6 mg iv). The responses in total electromechanical systole (QS2), the heart sounds interval (S1S2), and the pre-ejection period (PEP) proved to be a more constant and specific measure of the digitalis effect than other hemodynamic responses. Abbreviation in the left ventricular ejection time (LVET) was less consistent than that in the other systolic time intervals. The changes in PEP and LVET, after correction for heart rate, correlated significantly with each of the hemodynamic responses (cardiac output, cardiac work, stroke volume, stroke work, mean stroke power, mean rate of left ventricular ejection, mean arterial and pulse pressure). In contrast, the responses in QS2and S1S2did not correlate significantly with any hemodynamic measure. Serial observations of the systolic intervals permitted description of the sequential development of the digitalis response. Maximum abbreviation in all of systolic intervals occurred within 40 minutes of drug administration. The rate of onset of the response to cedilanid-D was the same in the patients as in normal individuals. The systolic time intervals offer a conveniently derived noninvasive measure of the cardiac response to digitalis in patients with congestive heart failure. The changes in the PEP and LVET are conditioned by the overall hemodynamic response and can be applied as a measure of the magnitude of change in the cardiac output and stroke parameters.