This study evaluates the effects of a standardized meal on cardiovascular hemodynamics in 12 patients with New York Heart Association Class III congestive heart failure. This was done as part of a larger study in which an orally active dopaminergic agonist was given on two mornings, once with a standardized breakfast and once fasting, and one morning a placebo was given with the breakfast. The order of days was randomized. Hemodynamic data were obtained over 8 h each day. There were significant changes in several hemodynamic variables after the placebo-food regimen lasting up to 1.5 h: cardiac index rose from 1.8 +/- 0.4 to 2.2 +/- 0.5 L/min.m2 at 30 min (p less than .001) and to 2.0 +/- 0.5 L/min.m2 at one hour (p less than .05); stroke volume index rose from 20 +/- 7 to 24 +/- 7 ml/min at 30 min (p less than .05) and to 23 +/- 7 ml/min at one hour (p less than .05); systemic vascular resistance fell from 1890 +/- 685 to 1534 +/- 497 dyne.sec/cm5 at 30 min (p less than .001) and to 1668 +/- 524 dyne.sec/cm5 at one hour (p less than .05). Mixed venous oxygen saturation was measured continuously in seven patients and rose significantly at one and 1.5 h. We conclude that food ingestion can have a significant effect on cardiovascular hemodynamics and that this effect should be considered when therapeutic effects are to be guided by invasive hemodynamic monitoring in this population.