Eight healthy people (seven men and one woman, aged 19 to 31 years) were studied by radionuclide cardiography when supine before and 30 minutes after a standard meal (6300 kJ). Control investigations were performed on a different day within a week of the standard meal. There was a median increase in cardiac output of 62% that was attributable to a 17% increase in heart rate and a 41% increase in stroke volume. Blood pressure and concentrations of plasma catecholamines did not change. The median end diastolic and end systolic volumes of the left ventricle increased by 41% so that the left ventricular ejection fraction was unchanged. There were no significant changes during the control experiments. In healthy people a meal caused an appreciable increase in stroke volume and dilatation of the left ventricle. The activity of the sympathetic nervous system, as measured by plasma catecholamines, did not change much, and changes in blood volume alone did not seem to explain the haemodynamic response to the meal.