Introduction and objectives: The long-term prognostic significance of coronary artery dominance pattern in patients with ST-segment elevation myocardial infarction is poorly characterized. We investigated the prognosis of such patients according to whether they had right dominance, left dominance, or codominance. Methods: This was a retrospective study of 767 patients, who were admitted to hospital between 2007 and 2012 with ST-segment elevation myocardial infarction and treated with primary percutaneous coronary intervention. We determined the effect of the coronary dominance pattern on all-cause mortality and readmission for infarction, adjusting for mortality as a competing event. Results: A total of 80.9% of patients had right coronary dominance, and 8.6% had left coronary dominance. Over 40.8 months' [interquartile range, 21.9-58.3 months] follow-up, 118 (15.4%) deaths were recorded, of which 39 (5.1%) were in hospital. Mortality for right dominance, left dominance, and codominance was 7.1%, 36.4%, and 13.8% (P < .001), respectively. Cause of death was cardiovascular in 7.1%, 21.2%, and 2.4%. On Cox multivariate analysis, left dominance was significantly associated with mortality (hazard ratio = 1.76; P = .02). Taking "coronary dominance" into account in prediction of risk of death improved the discrimination and calibration capacity of GRACE (Global Registry of Acute Coronary Events) scoring. At follow-up, 9.3% (71 patients) had reinfarction. On multivariate analysis, left dominance was an independent predictor of reinfarction (subhazard ratio = 2.06; P = .01). Conclusions: In ST-segment elevation myocardial infarction treated with primary percutaneous coronary intervention, left coronary artery dominance confers a higher risk of death and reinfarction than right coronary artery dominance, and should be included in prognostic stratification. (C) 2015 Sociedad Espanola de Cardiologia. Published by Elsevier Espana, S.L.U. All rights reserved.