Appropriate use of a thrombolytic agent may save 20 to 30 lives per 1000 treatments. Thrombolysis should be considered in all patients presenting with cardiac chest pain lasting more than 30 minutes for up to 12 hours after symptom onset. ECG criteria include ST elevation of at least 1 mm in limb leads and/or at least 2 mm in two or more adjacent chest leads or left bundle branch block. There is no upper age limit. All patients should also receive oral aspirin and subcutaneous (intravenous with rt-PA) heparin. Other adjuvant treatments have been reviewed previously in this journal. Streptokinase is the drug of choice except where there is persistent hypotension, previous streptokinase or APSAC at any time, known allergy to streptokinase, or a recent proven streptococcal infection. In these circumstances the patient should receive rt-PA. Additional indications for rt-PA, based on subset analysis by the GUSTO investigators, include patients with ALL of the following: age less than 75 years, presentation within four hours of symptom onset, and ECG evidence of anterior acute myocardial infarction. Treatment should be initiated as soon as possible. The greatest benefit is observed in patients treated early, pain to treat intervals of less than one hour make possible mortality reductions of nearly 50%. "When" matters more than "where": fast tracking to the CCU is one option but A&E initiated thrombolysis is feasible and timely. Prehospital thrombolysis is appropriate in certain geographical situations. The development of practical guidelines for thrombolysis represents the most comprehensive example of evidence based medicine. Streptokinase was first shown to influence outcome in acute myocardial infarction nearly 40 years ago. More recently alternative regimes have been evaluated in several prospective randomised controlled trials yielding pooled data on nearly 60,000 patients. However, systematic review of cumulative data reveals a statistically significant mortality gain for intravenous streptokinase over placebo which could have been identified as early as 1971-at least 15 years before it became generally used in clinical practice.