Ten minutes of total cerebral ischaemia was produced in normo- and hypoglycaemic rats. The most conspicuous findings were loss of hippocampal (CA-1) pyramidal cells and Purkinje cells, which were most pronounced in the normoglycaemic rats. While pre-ischaemic hypoglycaemia to some extent protected these cells, it led to infarction of severe ischaemic nerve cell changes in the brain stem nuclei and lowered the neurological restitution of the hypoglycaemic animals. The regional damage in these rats, which were kept normotensive after ischaemia, was not due to circulatory insufficiency. However, rats with untreated spontaneous low blood pressure in the early postischaemic period showed multiple small infarcts.