BACKGROUND Near-infrared spectroscopy is a potential tool for measuring adequacy of cerebral oxygenation during cardiac operations. The cerebral microcirculation is predominantly venous (by volume) and therefore regional cerebral oxygenation measured by near-infrared spectroscopy should reflect jugular bulb venous saturations. METHODS We compared simultaneous regional cerebral oxygenation and jugular bulb venous saturation measurements in 40 children (median age, 4.5 years; range 2 weeks to 14.5 years) in the cardiac catheter laboratory (n = 29) and during cardiac operations (n = 11). RESULTS For all patients combined the correlation between regional cerebral oxygenation and jugular bulb venous saturation was 0.69 (p < 0.0001) and was similar for the two groups. For individual children undergoing cardiac operations excellent correlations were obtained (r = 0.78 to 0.96; median, 0.91). However, at low values of jugular bulb venous saturation, regional cerebral oxygenation tended to run high, whereas the converse was true for high values of jugular bulb venous saturation. CONCLUSIONS These findings suggest that near-infrared spectroscopy may be a useful tool for assessing intravascular cerebral oxygenation during pediatric cardiac operations. Prospective studies of neurologic outcome will be required to establish the value of this technique for assessing the adequacy of cerebral protection.