Measurements of cerebral oxygen consumption (CVO2) may improve our understanding of cerebral oxygenation, but there are few published data for sick neonates. Although cerebral maturation is associated with an increase in cerebral glucose consumption, the relationship between CVO2 and increasing gestational age has not previously been assessed in humans. The aims of this study were to evaluate a noninvasive method for the estimation of CVO2 in the neonate using near infrared spectroscopy, and to investigate the relationship between gestational age and CVO2. Twenty babies who were undergoing intensive care in the neonatal period were studied. Cerebral hemoglobin flow (CHbF) and cerebral venous oxyhemoglobin saturation (CSVO2) were measured using near infrared spectroscopy. Arterial oxyhemoglobin saturation was measure by pulse oximetry (SpO2). CVO2 was calculated from the equation: CVO2=CHbF x (SpO2 - SvO2 x 4. The median (range) CVO2 was 0.9 (0.52-1.76) mL x 100 g(-1) min(-1). There was an increase in CVO2 with advancing gestational age (n=20, p=0.55, p=0.014). We conclude that CVO2 can be estimated in sick neonates using noninvasive optical methods. The values obtained are similar to those obtained in other studies by more invasive methods, and are in agreement with values which would be expected from the known rate of cerebral glucose consumption in neonates. Mean (SD) CVO2 at 24-26 wk was 0.5 (0.18) mL x 100 g(-1) min(-1) and rose with increasing gestation to term by 0.03 mL x 100 g(-1) min(-1) per wk.