To determine a risk profile of deterioration in cerebral infarction of less than 8 hours' duration, we studied prospectively a series of clinical and radiologic data in 98 patients. We evaluated the Canadian Neurological Scale Score and Barthel index during a follow-up period of 3 months. There was deterioration in the 1st 48 hours in 40.8% of the patients. High systolic blood pressure, elevated blood sugar concentration at admission, and carotid territory involvement were independently related with deterioration in the logistic regression analysis. Death occurred in 35% of the patients with deteriorating infarcts and in 8.6% of those with stable infarcts. At the end of the study, functional capacity was lower in those with deteriorating infarcts, but the 2 groups improved in parallel from the 4th day onward.