Cardiac output is a determinant of systemic blood flow and its measurement may therefore be a useful indicator of abnormal hemodynamics and tissue oxygen delivery. The purpose of this study was to investigate in very premature newborn infants the relationships between cardiac output (left and right ventricular outputs), systemic blood pressure, peripheral blood flow (PBF) and two indicators of cerebral oxygen delivery (cerebral electrical activity and cerebral fractional oxygen extraction (CFOE)). This was a prospective observational study performed on 40 infants of less than 30 wk gestation. Digital electroencephalograms (EEGs) were recorded for one hour every day during the first four days after birth and subjected to qualitative and quantitative analysis. Left and right ventricular outputs, mean blood pressure (MBP), CFOE, PBF and arterial blood gases were measured at the same time. Within the ranges studied, there was no apparent relationship between left or right ventricular output (RVO), PBF and indicators of cerebral perfusion (cerebral electrical activity and CFOE). The EEG was normal in infants with low left and right ventricular outputs (<150 mL/kg/min) and MBP > 30 mm Hg. Infants with low cardiac output and normal MBP seem able to maintain cerebral perfusion, possibly through vasodilatation of the cerebral microvasculature.