This study was performed to evaluate the possibility of early identification of patients with an acute coronary syndrome who are transported by ambulance. All patients in the community of Göteborg who were transported by ambulance over a period of 3 months owing to symptoms raising any suspicion of an acute coronary syndrome were studied. In all 930 cases that were included in the survey, 130 (14%) had a final diagnosis of acute myocardial infarction (AMI) and 276 (30%) had a final diagnosis of an acute coronary syndrome. Independent risk indicators for development of AMI were: male sex (odds ratio 1.70; 95% confidence limits 1.02-2.84), cold and clammy on admission of the ambulance crew (odds ratio 2.07; 95% confidence limits 1.23-3.49) and showing electrocardiogram (ECG) signs of myocardial ischemia on admission to the emergency department (odds ratio 8.78; 95%confidence limits 5.28-14.61). Independent predictors for development of an acute coronary syndrome were: male sex (odds ratio 1.97; 95% confidence limits 1.30-2.99), a history of angina pectoris (odds ratio 3.41; 95% confidence limits 2.24-5.26), cold and clammy on admission of the ambulance crew (odds ratio 1.95; 95% confidence limits 1.21-3.15), and ECG signs of myocardial ischemia on admission to the emergency department (odds ratio 5.55; 95% confidence limits 3.63-8.58). Among patients seen by the ambulance crew with symptoms raising any suspicion of an acute coronary syndrome, predictors for that diagnosis included male sex, a history of angina pectoris, patients being cold and clammy on admission of the ambulance crew, and ECG signs of myocardial ischemia on admission to the emergency department.