Introduction: Near Infrared Spectroscopy (NIRS) measures of brain oxygenation (SctO2) may provide a surrogate marker of cortical ischemia but there is a lack of evidence to support its clinical utility. If NIRS correlates with neurophysiological measures of cortical ischaemia it may be used to guide therapy. Objectives: Explore the relationship between NIRS, somatosensory evoked potentials (SSEPs) and electroencephalography (EEG) when used to monitor critically ill children. Methods: NIRS, SSEP & EEG data were prospectively recorded at the initiation, weaning and in a stable period of extracorporeal membrane oxygenation (ECMO) therapy in 6 patients. Results: 85% of recordings contained no clinically significant deviations. Synchronised decreases in NIRS SctO2 with preceding EEG power; SSEP amplitude & EEG power increase in the absence of significant NIRS change were seen in 15%. Asymmetries were seen in all patients, particularly in trans-thoracic cannulated patients [n= 2]. Over the course of ECMO therapy, NIRS SctO2, and total EEG power increased, delta/theta ratio decreased and there was a significant difference in all device measurements between patients alive and dead 30 days post ECMO initiation. Conclusions: Correlations between the three devices appear to exist and neurophysiological measures of cortical function may precede or go undetected by NIRS; however more data is needed before accepting the alternate hypothesis.