The shock index (IS) is the quotient between the heart rate (HR) and the systolic blood pressure (SBP) (IS: HR / SBT), and the age-adjusted shock index (ISA) multiplying the IS by age. We evaluated its predictive value for the combined in-hospital event (EC), death and / or cardiogenic shock (CS) and for individual events in the patients included in the Argentine registry of ST-segment elevation infarction (ARGEN-ST-AMI); 248 with CS on admission were excluded. ROC curves were made for both indices using the best cut-off point to dichotomize the population. The analysis included 2928 subjects. Age (median) 60 years (IQR 25-75% 53-68), men 80%, EC: 6.4%; 30.5% had IS = 0.67, and they had a higher incidence of EC: 11% vs. 4% (p < 0.001), cardiogenic shock (8% vs. 2.6%, p <0.0001) and death (7.3% vs. 3%), p <0.0001) than patients with IS < 0.67. A 28% had ISA = 41.5. These presented plus EC: 14% vs. 3%, p < 0.001, SC: 10% vs. 2%, (p < 0.001) and death: 9.5% vs. 2.3%, (p < 0.001) compared with patients with values < 41.5. The area under the ROC curve of the ISA for EC was significantly better than that of the IS (0.72 vs. 0.62, p < 0.001). In the multivariate analysis models performed, the IS had an OR: 2.56 (95% CI 1.56-4.02; p < 0.001) and the ISA: 3.43 (95% CI 2.08-5.65; p < 0.001) for EC. The IS and ISA predict death and / or the development of in-hospital cardiogenic shock in an unselected population of ST elevation infarcts.