Sex and gender differences in the presentation and outcome of acute coronary syndromes (ACS) are substantial. Despite the growing body of evidence for excess cardiovascular vulnerability in female patients, a persistent knowledge gap is nourished by the underrepresentation of women in clinical ACS trials. Intriguingly, increasing mortality rates have recently been reported for young women <55 years of age. This review provides an overview of the contemporary evidence for sex and gender differences in vascular biology, clinical presentation and outcomes of ACS.