Objective. To determine the prognostic significance of indices of platelet aggregation (PA) and the level of interleukin IL-1β in the outcome of ischemic stroke (IS). Material and methods. One hundred and eight patients were studied. According to disease outcome, two groups of patients were identified: survivors (group 1) and patients with fatal outcome (group 2). Patients were examined in the very early stage (the 1st day of hospitalization) and in the early stage (the 7th day of hospitalization) of IS. The level of interleukin IL-1β in blood serum was defined by enzyme immunoassay method. PA was measured by nephelometric method. Results and сonclusion. According to PA indices, a posteriori prognosis of fatal outcome was 10%, but according to IL-1β indices, it was 0.90%. Consequently, the prognostic significance of PA indices with regard to fatal outcome of IS patients in the acute period is higher than that of IL-1b indices. Taking into consideration the expenses of both methods of diagnosis, the authors conclude that with regard to economic availability, PA measurement as a prognostic-diagnostic method is more acceptable in clinical practice.