 However complications after both reperfusion treatment modalities such as symptomatic intracerebral hemorrhage, malignant brain oedema, re-occlusion, infection, and seizures may occur. Unfortunately few clinical signs provide prognostic information for clear risk stratification. The guidelines for reperfusion therapies in Switzerland, Europe and the US do not include -for the time being- biomarkers in the decision-making-process. However there might be powerful biomarkers, which can serve as point of care tools for the risk stratification of candidates to receive thrombolysis. Plasma copeptin concentration has recently been shown to be an easy to determine, steady parameter which independently predicts functional outcome and death in patients with an acute ischemic stroke. Copeptin derives from a larger precursor peptide pre-provasopressin along with two other peptides, Vasopressin AVP and neurophysin II. Released in an equimolar ratio, the amount of copeptin mirrors the production of AVP. AVP plays an important role in the regulation of the hypothalamo-pituitary-adrenal HPA axis and, thus, reflecting the individual stress response. Stressors such as stroke are strong stimulators of the release of AVP. The close and reproducible relation of copeptin levels to the degree of activation of the stress axis is the basis of its usefulness as a biomarker. Early prognostic factors to predict mortality and outcome in stroke patients are important to guide and tailor early decision on treatment. In this context, copeptin may be helpful tool in the early risk stratification of stroke patients to guide the decision for reperfusion therapies. 