The influence of diabetes mellitus and hyperglycemia on cerebral infarction has been studied on 77 patients who died of infarcts in the territory of the middle cerebral artery. The size of the infarcts was assessed by transferring the surface of the infarcted area onto 8 schematic drawings corresponding to 8 brain slices and measuring this surface by means of a planimeter. An infarction volume index (IVI) was calculated by measuring the ratio of the infarcted area to the theoretical area of the middle cerebral artery territory on the 8 slices. The causes of death were assessed by full post-mortem examination. There was no statistically significant difference in size of infarcts and causes of death between diabetics and non-diabetics. However, the stroke-to-death interval was shorter (p = 0.05) in non-diabetic patients. It appears from this study that diabetes mellitus has no deleterious effect on cerebral infarction. Equally, there were non statistically significant differences in size of infarcts, stroke-to-death interval and causes of death between patients with and without hyperglycemia.