Despite early revascularization, mortality remains high in patients with ST-segment elevation myocardial infarction (STEMI) complicated by cardiogenic shock. It has been shown that the effect of multivessel disease (MVD) on mortality in patients with STEMI treated with primary percutaneous coronary intervention is mainly caused by the presence of chronic total occlusion (CTO) in a noninfarct-related coronary artery. Whether this association also exists in patients with STEMI with cardiogenic shock is unknown. In our institution, 292 consecutive patients with STEMI complicated by cardiogenic shock were admitted from 1997 to 2005 and treated with primary percutaneous coronary intervention. Patients were classified as having single vessel disease, MVD without CTO, and CTO. Cox regression analysis was used for multivariate analysis. The 1-year mortality rate of patients with single-vessel disease, MVD, and CTO was 31%, 47%, and 63%, respectively. After adjustment for possible confounders, MVD alone was not an independent predictor of 1-year mortality (hazard ratio 1.5, 95% confidence interval 0.98 to 2.3, p = 0.07). In contrast, CTO in a noninfarct-related artery was an independent predictor of 1-year mortality (hazard ratio 2.1, 95% confidence interval 1.5 to 3.1, p <0.01). In conclusion, the presence of CTO in a non–infarct-related artery was an independent predictor of 1-year mortality. In contrast, MVD alone lost its predictive significance after multivariate analysis.