The doctoral thesis consists of three original articles, which are thematically coherent collection of research papers that examined the prognostic significance of hyperfibrynogenemia in ischemic stroke patients. The aim of our first study was to determine if the sustained increase of plasma fibrinogen during the first two weeks after a stroke predicts outcome independently of baseline fibrinogen concentration. Results: the sustained increase of plasma fibrinogen during ischemic stroke predicts worse outcome independently of baseline fibrinogen level. The aim of our second study was to determine the relationship between plasma fibrinogen level and long-term risk of death in ischemic stroke patients. Results: hyperfibrinogenemia predicts the long-term risk of death in ischemic stroke patients. The aim of our third study was to determine the prognostic value of plasma fibrinogen for the prediction of functional outcome after ischemic stroke. Results: the addition of fibrinogen to predictive model including age and stroke severity does not improve discrimination between favorable and unfavorable outcomes after ischemic stroke.