Background: Despite data showing that time to treatment is very important in ST-elevation myocardial infarct patients, unacceptable long delays to reperfusion remain present in daily life practice. We sought to evaluate the feasibility and effect of improving logistics by early infarct diagnosis in the ambulance and immediate triage to a percutaneous coronary intervention(PCI) center performed by paramedics only without interference of a physician. Methods: In the On-TIME study, 209 patients were included after prehospital infarct diagnosis and triage in the ambulance(ambulance group, n=209). Infarct diagnosis was made by highly trained paramedics with the help of a computerized electrocardiographic algorithm. The accuracy of diagnosis, time to treatment, left ventricular function, and clinical outcome were compared with the patients who were diagnosed and triaged at a referral non-PCI center(referred group, n=258). Left ventricular function was assessed before discharge using a nuclear technique. Results: Acute myocardial infarction was accurately diagnosed in 95%of patients in the ambulance group, as compared with 99%in the referred group(P=.01). The percentage of patients in whom pharmacologic pretreatment(heparin, aspirin, tirofiban, or placebo) was initiated in the ambulance within 90 minutes after the onset of symptoms was 59%in the ambulance group versus 43%in the referred group(P< .01). A left ventricular ejection fraction of< 40%was present in 25%in the ambulance group, as compared with 38%in the referred group(P=.013). After multivariate analysis, ambulance triage was independently associated with a left ventricular ejection fraction >40%and a favorable longterm clinical outcome. Conclusions: Early, prehospital infarct diagnosis, triage, and therapy in the ambulance with direct transportation to the nearest PCI center, performed by trained paramedics only, is feasible in 95%of patients. Ambulance triage resulted in earlier diagnosis and initiation of therapy and was independently associated with a better left ventricular function and clinical outcome, as compared with triage and transportation from a referral non-PCI center. Background: Despite data showing that time to treatment is very important in ST-elevation myocardial infarct patients, unacceptable long delays to reperfusion remain present in daily life practice. We sought to evaluate the feasibility and effect of improving logistics by early infarct diagnosis in the ambulance and immediate triage to a percutaneous coronary intervention (PCI) center performed by paramedics only without interference of a physician. Methods: In the On-TIME study, 209 patients were included after prehospital infarct diagnosis and triage in the ambulance (ambulance group, n = 209). The accuracy of diagnosis, time to treatment, left ventricular function, and clinical outcome were compared with the patients who were were diagnosed and triaged at a referral non -PCI center (referred group, n = 258). Left ventricular function was assessed before discharge using a nuclea r technique. Results: Acute myocardial infarction was accurately diagnosed in 95% of patients in the ambulance group, compared with 99% in the referred group (P = .01). The percentage of patients in whom pharmacologic pretreatment (heparin, aspirin, tirofiban, or placebo) was initiated in the ambulance within 90 minutes after the onset of symptoms was 59% in the ambulance group versus 43% in the referred group (P <.01). A left ventricular ejection fraction of <40% was present After multivariate analysis, ambulance triage was independently associated with a left ventricular ejection fraction> 40% and a favorable longterm clinical outcome. Conclusions : Early, prehospital infarct diagnosis, triage, and therapy in the ambulance with direct transportation to the nearest PCI center, performed by trained paramedics only, is feasible in 95% of patients. Ambulance triage resulted in earlier diagnosis and initiation of therapy and was independently associated with a better left ventricular function and clinical outcome, as compared with triage and transportation from a referral non-PCI center.