Early reperfusion in acute myocardial infarction has been shown to reduce myocardial damage and to improve prognosis. The goals of this study, the Olten Cardiac Emergency Study, were to identify the factors, related to the patients or to the emergency medical services, which influenced pre-hospital delay in patients with symptoms suggestive of acute myocardial infarction. From November 1, 1992, to June 15, 1993, all the events occurring between symptom onset and hospital discharge where analyzed for 341 such patients who were cared for by the emergency networks connected with the Cantonal Hospital, Olten: in addition, follow-up at 3 months was obtained on all patients discharged alive. Of the 341 patients, 14 (4.1%) died out of the hospital. The final diagnoses of the 327 patients admitted to the emergency department were: acute myocardial infarction 18.3%; unstable angina 10.1%; stable angina 3.4%; non-ischemic cardiac diseases 29.4%; other non-cardiac diseases 38.8%. Mean delay between symptom onset and arrival at the hospital was 8 h 55 min (median delay 4 h 10 min); for patients with a final diagnosis of acute myocardial infarction, mean delay was 9 h 43 min (median delay 5 h 10 min). Patient delay was surprisingly long and represented 70.4% of the total pre-hospital delay; 56.6% of the patients did not realize that their symptoms were serious and only 47.1% (and 68.3% of the patients with acute myocardial infarction) came to the hospital by ambulance. These long pre-hospital delays were responsible for the low (13.3%) thrombolysis rate of patients with acute myocardial infarction. We conclude that pre-hospital delay was much too long in our population. Improvements can only be achieved through patient education and better efficiency of emergency networks. Our findings underline the need for public education campaigns on heart attacks.