AIM: To describe predictors of myocardial infarction prior to hospital admission in women and men among patients with a suspected acute coronary syndrome without ST-elevation. DESIGN: Prospective observational study in Stockholm and Göteborg, Sweden. RESULTS: Of 433 patients who did fulfill the inclusion criteria 45% were women. Fewer women (17%) than men (26%) developed acute myocardial infarction (AMI) (p=0.054), particularly among patients with initial ST-depression, in whom AMI was developed in 22% of women and 54% of men (p = 0.001). Predictors for infarct development in women were: a history of AMI and advanced age. Among men they were: initial ST-depression or a Q-wave on ECG and elevation of biochemical markers (both recorded on admission of the ambulance crew). There was a significant interaction between gender and the influence of ST-depression on the risk for development of myocardial infarction (p < 0.05). CONCLUSION: Among patients transported with ambulance due to a suspected acute coronary syndrome and no ST-elevation fewer women than men seem to develop AMI particularly among patients with ST-depression. These results suggest that early prediction of myocardial infarction might differ between women and men with acute chest pain.