One-hundred fifty-two patients with a diagnosis of stroke were routinely admitted to the hospital and studied by bilateral carotid and vertebral arteriography. Complication rate was 3.5%. Obstructive lesions were seen in 95% of cases. Incidence and location of atherosclerosis and associated disease, age, sex, racial factors, surgical accessibility, and results of medical and surgical treatment were evaluated. Surgical reconstruction was performed in 13.2%. Fifteen per cent of patients died, 20% worsened neurologically, 35% improved, and 30% were unchanged. Medical treatment is best adjusted to each patient. Oxygen therapy, adequate airway, hydration, nutrition, and optimum cardiac output are important in acute strokes. Anticoagulant plus fibrinolysin therapy has produced clot lysis, demonstrated by arteriography, and clinical assessment of a double blind-treated series of 40 patients has shown that this form of treatment can be carried out without danger.