OBJECTIVE In acute myocardial infarction, cardiovascular magnetic resonance (CMR) allows for quantifying the extent of salvaged myocardium after reperfusion as a potential strong end point for clinical trials. The aim of this study was to investigate whether the early prognostic significance of myocardial salvage assessed by CMR is sustained at long-term clinical follow-up in patients with ST-elevation myocardial infarction (STEMI) undergoing primary angioplasty. METHODS We analysed 208 consecutive patients with STEMI undergoing primary angioplasty <12 h after symptom onset. T2-weighted and contrast-enhanced CMR was used to calculate the myocardial salvage index (MSI). Patients were categorised into two groups defined by the median MSI. The primary end point was the occurrence of major adverse cardiovascular events defined as death, reinfarction and new congestive heart failure at long-term follow-up. RESULTS The median MSI was 48 (IQR 27 to 73). Long-term follow-up was available in 202 patients (97%) at a median of 18.5 months (IQR 13.8 to 20.8). Major adverse cardiovascular events occurred in 33 patients (16%), with a significantly lower event rate in the MSI ≥ median group (7 vs 26 events, p<0.001). Mortality was significantly reduced in the MSI ≥ median group (2 vs 12 deaths, p = 0.001). MSI was a significant independent predictor for a favourable long-term survival on multivariable Cox regression analysis after adjustment for established prognostic markers. CONCLUSIONS MSI assessed by CMR predicts long-term clinical outcome in acute reperfused STEMI. Therefore, our data support the use of myocardial salvage as an end point for clinical trials investigating novel reperfusion strategies. Trial registration number http://www.ClinicalTrials.gov: NCT00952224.