The purpose of the work was to assess the insulin secretion after a glucose load in a group of patients with cerebral infarction and in a group of arteriosclerotic and hypertonic patients, i.e. potential candidates of cerebral infarction. The material comprised 46 patients, incl. 29 with focal cerebral ischaemia and 17 with arteriosclerosis and hypertension. After oral glucose administration plasma insulin was assessed by radiooimmuncassay (IRI). It was revealed that insulinsecretion in the group of hypertonic and arteriosclerotic patients follows the rise of the blood sugar level, the rise is somewhat lower than in the control group but persists longer and returns later to baseline values. Similar but quantitatively more marked changes were refealed also in the group with focal cerebral ischaemia. From the results ensues that a reduced glucose tolerance in patients with cerebral infarction recorded in previous work is not due to an inadequate insulin secretion, i.e. the peripheral glucose metabolism, but indicates rather the ineffectiveness of insulin to restore glucose homeostasis.