Objectives: To study sex-based differences in the clinical presentation in relation to age and type of acute coronary syndrome (ACS) in patients under 80 years of age. Methods: The study includes 1,744 consecutive patients with the full spectrum of ACS (ST elevation myocardial infarction (MI), non-ST elevation MI, and unstable angina of high- and low-risk types) admitted to the coronary care unit in a university hospital. Results: The women were older than the men and were as likely to present with ST elevation MI. They had lower rates of prior MI and prior coronary artery bypass surgery than men but similar rates of percutaneous coronary interventions. Further, women were less likely to have a short delay before admission to hospital and they were attended to less rapidly in the emergency department. The prevalence of risk factors, prior cardiovascular disease and ongoing treatment with cardiovascular drugs were strongly associated with less severe type of ACS with no significant sex interaction. Presentation with non-ST elevation MI was significantly associated with older age while the opposite was true for unstable low-risk angina. ECG signs of acute ischemia were not associated with age. Significant interactions between age and sex were observed for the prevalence of treatment with diuretics as well as hypotension at presentation, both more prevalent among women than men below 65 years of age. Conclusions: Women are struck by ACS at a higher age than men, are less likely to present early for hospital care, and at younger age women are more likely to present with hypotension. There is a striking difference in risk factors and previous history depending on type of ACS in both sexes.