BACKGROUND: Cardiogenic shock (CS) is a serious complication of acute myocardial infarction, and the time of onset of CS has a potential role in influencing its prognosis. Limited contemporary data exist on this complication, however, especially from a population-based perspective. Our study objectives were to describe decade-long trends in the incidence, in-hospital mortality, and factors associated with the development of CS in 3 temporal contexts: (1) before hospital arrival for acute myocardial infarction (prehospital CS); (2) within 24 hours of hospitalization (early CS); and (3) > /=24 hours after hospitalization (late CS). METHODS AND RESULTS: The study population consisted of 5782 patients with an acute myocardial infarction who were admitted to all 11 hospitals in central Massachusetts on a biennial basis between 2001 and 2011. The overall proportion of patients who developed CS was 5.2%. The proportion of patients with prehospital CS (1.6%) and late CS (1.5%) remained stable over time, whereas the proportion of patients with early CS declined from 2.2% in 2001-2003 to 1.2% in 2009-2011. In-hospital mortality for prehospital CS increased from 38.9% in 2001-2003 to 53.6% in 2009-2011, whereas in-hospital mortality for early and late CS decreased over time (35.9% and 64.7% in 2001-2003 to 15.8% and 39.1% in 2009-2011, respectively). CONCLUSIONS: Development of prehospital and in-hospital CS was associated with poor short-term survival and the in-hospital death rates among those with prehospital CS increased over time. Interventions focused on preventing or treating prehospital and late CS are needed to improve in-hospital survival after acute myocardial infarction.