peer reviewed ; Aims: To determine whether there are gender-based differences in in-hospital outcomes among patients undergoing percutaneous coronary intervention (PCI). Methods and results: We studied a large cohort using clinical data from a registry of 130,985 PCI procedures in Belgium, from January 2006 to February 2011. Compared to males, females were significantly older (70.3 vs. 64.8 years), and were more frequently diabetic or hypertensive. Men smoked more and more frequently had previous myocardial infarction (MI), previous PCI or previous coronary artery bypass graft (CABG) surgery. Coronary artery disease (CAD) was less severe in women, and PCI to the left anterior descending artery was more common in female patients. Unadjusted in-hospital mortality rates were higher in females versus males (2.5% for women and 1.6% for men, p<0.0001). After multivariable analysis, female gender remained an independent predictor of mortality (odds ratio 1.35, 95% CI: 1.22-1.49, p<0.0001). Conclusions: Gender-based differences in hospital mortality rates after PCI were observed in this large registry. Female sex remained an independent predictor of mortality after multivariable adjustment.