Admission hyperglycemia is associated with high inhospital and long-term adverse events in patients that undergo primary percutaneous coronary intervention (PCI). We aimed to evaluate whether hyperglycemia predicts inhospital mortality. We prospectively analyzed 503 consecutive patients. The patients were divided into tertiles according to the admission glucose levels. Tertile I: glucose < 118 mg/dL (n = 166), tertile II: glucose 118 to 145 mg/dL (n = 168), and tertile III: glucose > 145 mg/dL (n = 169). Inhospital mortality was 0 in tertile I, 2 in tertile II, and 9 in tertile III (P < .02). Cardiogenic shock occurred more frequently in tertile III compared to tertiles I and II (10% vs 4.1% and 0.6%, respectively, P = .01). Multivariate logistic regression analysis revealed that patients in tertile III had significantly higher risk of inhospital major adverse cardiac events compared to patients in tertile I (odds ratio: 9.55, P < .02). Admission hyperglycemia predicts inhospital adverse cardiac events in mortality and acute ST-segment elevation myocardial infarction in patients that underwent primary PCI.