The E-MUST registry gathers patient data from the emergency ambulance service of the IIe-de-France for acute coronary syndromes with ST elevation seen within 24 hours from onset of symptoms. The parameters include the type of emergency phone call, details relative to the different phase of management, decisions of therapeutic strategy concerning pre-hospital thrombolysis or primary angioplasty and the different factors influencing these decisions. From January 2001 to June 2002, the mean delay from the onset of symptoms and the call-out of the emergency ambulance was 67.5 minutes for the 2584 patients studied. In this group, a pre-hospital decision for coronary revascularisation was taken in 84.3% of cases, pre-hospital thrombolyis started 33 minutes after arrival of the ambulance (32.7% of cases) and primary angioplasty carried out 81 minutes after that arrival (51.6% of cases). Decisions for revascularisation were less common in the elderly and those seen over 6 hours after the onset of symptoms. Pre-hospital management allows decisions concerning coronary reperfusion to be taken more often and earlier in patients with acute coronary syndromes.