Hyperglycemia is correlated with poor prognosis in ischemic strokes and also increases the risk of hemorrhagic transformation after thrombolysis. The toxicity of hyperglycemia, already well established in animals, is beginning to be clear for humans. On the other hand, the beneficial effect of insulin remains controversial in animals and has never been demonstrated in humans. Preliminary data, which suggest that the speed and quality of glycemic control may be decisive in the efficacy of treatment, merit testing in a randomized trial.