Neuroprotective therapy is likely to be most effective in preventing or minimizing the effects of cerebral ischaemia when given as early as possible after the insult. Neuropsychological testing is the gold standard for assessing minor cerebral damage, but is carried out several days or weeks after surgery and is too late to be useful for instituting therapy. Current intraoperative cerebral monitors (EEG, CFAM, NIRS and TCD) can detect cerebral ischaemia with good sensitivity, and give immediate results, but their specificity for ischaemia is low. Biochemical markers offer the possibility of rapid and specific diagnosis of cerebral ischaemia which would allow the early institution of neuroprotective therapies.