Background: Sex differences in acute coronary syndrome (ACS) have been reported, but little is known about the situation in the Netherlands. Methods: This registry is a merge of available data on ACS patients in the electronic data capture systems of 11 centres with 24/7 interventional cardiology services. We included patients >18 years undergoing a cardiac catheterisation between 2010–2012. We evaluated sex differences in clinical and procedural characteristics and 1‑year mortality. Results: A total of 29,265 ACS patients (8,720 women and 20,545 men) were registered. Women were on average 4.5 years older (68.5 vs 63.0 years, p < 0.001) and had a higher prevalence of hypertension (62.7 vs 49.8%, p < 0.001) and insulin-dependent diabetes mellitus (9.6 vs 6.8%, p < 0.001) than men. Women less often presented with ST-elevation myocardial infarction (43.7% vs 47.6%, p < 0.001) and appeared to have less extensive coronary artery disease than men. Women less often underwent coronary angiography by radial access (52.5 vs 55.9%, p < 0.001). One-year mortality was higher in women than in men (7.3% and 5.6%, p < 0.001). More specific, the relationship between sex and mortality was age-dependent and showed higher mortality in women ≤71 years, but lower mortality in older women compared with men (p-interaction <0.001). Conclusion: We found differences in clinical and procedural characteristics and outcome between women and men admitted for ACS, which are in line with other Western countries. The limitations of our registry, based on existing local databases, can be overcome by the use of the prospective Netherlands Heart Registry that is currently in development.