Several studies have proven the usefulness of thrombolytic agents in the therapy of ischemic stroke. Data from open and small placebo-controlled trials show a relationship between recanalization and an improved clinical outcome. Three large scaled studies have examine the effect of streptokinase treatment. Because of an increasing mortality the results of these studies were negative, and so streptokinase should not be used to treat acute ischemic stroke. In contrast, three rt-PA studies with together more than 2000 patients showed a significant benefit. Recent meta-analyses including data of all these trials show an odds ratio for death and disability of 0.67 (95 p. 100 CI 0.56; 0.8). The number needed to treat to prevent one death or disability is 11 in a 6 hour time window and 7 in a 3 hour time window. These are impressive numbers that are rarely found in other areas of internal or neurological medicine. The most important risk of thrombolytic therapy is the occurrence of intracerebral hemorrhage, which is reported as between 0-18 p. 100, but which is not associated with increased morbidity or mortality. At present, thrombolytic therapy cannot be recommended for all patients with acute stroke. Careful selection and experiences with this therapy and its risks are necessary.