AIMS: The diagnosis of cardiogenic shock depends on clinical signs of poor perfusion and low blood pressure. Lactate concentration will increase with poor tissue perfusion, and it has prognostic value in cardiogenic shock patients. We sought to assess the prognostic value of lactate concentration in subjects admitted with suspected ST-elevation myocardial infarction (STEMI). METHODS AND RESULTS: In 2,094 (93%) out of 2,247 consecutive suspected STEMI-subjects, lactate concentration was measured on admission. The prognostic value of lactate concentration on 30-day mortality was assessed in addition to clinical signs of peripheral hypoperfusion, systolic blood pressure (sBP), and left ventricular ejection fraction (LVEF) in multivariable models.Lactate concentration added prognostic information beyond signs of peripheral hypoperfusion, sBP, and LVEF, and was independently associated with 30-day mortality (hazard ratio [95% confidence interval] 1.11 [1.07-1.14], P < 0.0001). Lactate also provided predictive information on 30-day mortality to the combination of signs of peripheral hypoperfusion, sBP, and LVEF (area under the receiver-operating characteristics curve = 0.88 vs. 0.83, P < 0.0001). CONCLUSIONS: In conclusion, admission lactate concentration in suspected STEMI-subjects contains prognostic information on 30-day mortality when added to variables used in cardiogenic shock-definition. We recommend lactate measurement in STEMI-subjects, especially when signs of compromised hemodynamics are present.