Even with the new fibrin-specific plasminogen activators thrombolytic therapy remains burdened with numerous side effects, some of them being severe or even life threatening, therapists being horrified if in rare cases the patient dies from severe haemorrhage subsequent to thrombolysis. The incidence and severity of bleeding increase with increasing aggressiveness of the therapeutic regimen and with increasing time during which the thrombolytic state is maintained. Furthermore, side effects related either to the plasminogen activator used (allergic reactions and systemic fibrinogen breakdown e.g.) or related to the underlying disease (pulmonary embolism and reperfusion arrhythmias e.g.) have to be considered. In order not to let thrombolysis become a double-edged sword, the risks of thrombolytic therapy should carefully be weighted against the benefits before thrombolysis is commenced.