This study was performed to examine the influence of time during the day and of meals on left ventricular performance in patients with dilated cardiomyopathy and chronic congestive heart failure. Systolic time intervals and echocardiography were performed at set intervals with concomitant hemodynamic measurements in nine patients with chronic congestive heart failure over a 15 hour daytime period and during the three meals. Pulmonary capillary wedge pressure decreased (p less than 0.05) from a non-meal resting peak of 18 +/- 8 mm Hg at 1500 hours to 16 +/- 7 mm Hg at 2200 hours. The other non-meal cardiovascular variables, invasive and noninvasive, did not change significantly during the course of the day. Cardiac output and stroke volume rose and pulmonary and systemic vascular resistances, systemic blood pressure, pulmonary artery pressure, and pulmonary capillary wedge pressure generally fell significantly after meals. Although mean PEP/LVET tended to decrease and delta p/delta t increase after meals, these numerical changes were not statistically significant and none of the other noninvasive variables were affected by meals. Patients with dilated cardiomyopathy and chronic congestive heart failure have modest changes in central hemodynamics over the course of a day with rather striking changes with food ingestion. These alterations are generally not reflected in noninvasive cardiovascular parameters.