The assessment of hypoxic–ischaemic brain injury (HIBI) remains predominantly clinical but ancillary support from investigations is important in improving sensitivity and specificity of neurological examination. 39 patients with HIBI admitted to an intensive treatment unit (ITU) over 5 years were reviewed retrospectively. There were 27 males, mean age 52.6 years. 10 patients had out-of-hospital arrest, 27 hypoperfusion during surgery or critical illness and two hypoxic insult. The outcome was poor, nine patients survived to discharge, five were severely disabled. The MRI changes evolved after severe insult. Characteristic patterns included early and extensive T2 high signal in the basal ganglia and thalamus following hypoxic insult. After prolonged cardiac arrest there was high signal in the caudate and putamen with restricted diffusion on ADC in the occipital region and peri-rolandic cortex. Following hypoperfusion, infarction in the watershed territories occurred with restricted diffusion and high signal on DWI, T2 and FLAIR. The pattern and extent of these changes correlate with outcome. The most important poor prognostic features on EEG included low voltage, poorly reactive rhythms, periodic lateralised epileptiform discharges and fluctuations in underlying rhythms. MRI and EEG are helpful adjuncts to clinical examination and can help to guide prognosis and management following HIBI.