Detailed neurohistological studies were undertaken on 35 cases of cardiac arrest, 17 of hypoglycaemia and 16 of status epilepticus. It was found that the frequency and pattern of selective vulnerability in the hippocampus were similar following cardiac arrest, hypoglycaemia and status epilepticus with the exception that the lateral limb of the dentate fascia was more frequently involved in hypoglycaemia than in the other two groups of cases. Within each group, however, CA1 was the most vulnerable. The cerebellum was less frequently affected in hypoglycaemia and status epilepticus than after cardiac arrest. These findings are compared with recent experimental studies in the rodent which have suggested that the pattern of neuronal damage in each of the three conditions is different.